diff --git a/backend/igny8_core/modules/billing/constants.py b/backend/igny8_core/modules/billing/constants.py
index 13f60131..428cddbe 100644
--- a/backend/igny8_core/modules/billing/constants.py
+++ b/backend/igny8_core/modules/billing/constants.py
@@ -1,22 +1,25 @@
 """
-Credit Cost Constants
+Credit Cost Constants - Phase 0: Credit-Only System
+All features are unlimited. Only credits restrict usage.
 """
 CREDIT_COSTS = {
-    'clustering': {
-        'base': 1,  # 1 credit per 30 keywords
-        'per_keyword': 1 / 30,
-    },
-    'ideas': {
-        'base': 1,  # 1 credit per idea
-    },
-    'content': {
-        'base': 3,  # 3 credits per full blog post
-    },
-    'images': {
-        'base': 1,  # 1 credit per image
-    },
-    'reparse': {
-        'base': 1,  # 1 credit per reparse
-    },
+    # Existing operations
+    'clustering': 10,                    # Per clustering request
+    'idea_generation': 15,              # Per cluster → ideas request
+    'content_generation': 1,             # Per 100 words
+    'image_prompt_extraction': 2,       # Per content piece
+    'image_generation': 5,              # Per image
+    
+    # Legacy operation names (for backward compatibility)
+    'ideas': 15,                        # Alias for idea_generation
+    'content': 1,                       # Alias for content_generation (per 100 words)
+    'images': 5,                        # Alias for image_generation
+    'reparse': 2,                       # Alias for image_prompt_extraction
+    
+    # NEW: Phase 2+ operations
+    'linking': 8,                       # Per content piece (NEW)
+    'optimization': 1,                  # Per 200 words (NEW)
+    'site_structure_generation': 50,    # Per site blueprint (NEW)
+    'site_page_generation': 20,         # Per page (NEW)
 }
 
diff --git a/backend/igny8_core/modules/billing/services.py b/backend/igny8_core/modules/billing/services.py
index 79a5651b..90719557 100644
--- a/backend/igny8_core/modules/billing/services.py
+++ b/backend/igny8_core/modules/billing/services.py
@@ -13,17 +13,49 @@ class CreditService:
     """Service for managing credits"""
     
     @staticmethod
-    def check_credits(account, required_credits):
+    def get_credit_cost(operation_type, amount=None):
+        """
+        Get credit cost for operation.
+        
+        Args:
+            operation_type: Type of operation (from CREDIT_COSTS)
+            amount: Optional amount (word count, etc.) for variable costs
+        
+        Returns:
+            int: Number of credits required
+        """
+        base_cost = CREDIT_COSTS.get(operation_type, 0)
+        
+        # Variable costs based on amount
+        if operation_type == 'content_generation' and amount:
+            # Per 100 words
+            return max(1, int(base_cost * (amount / 100)))
+        elif operation_type == 'optimization' and amount:
+            # Per 200 words
+            return max(1, int(base_cost * (amount / 200)))
+        
+        return base_cost
+    
+    @staticmethod
+    def check_credits(account, required_credits=None, operation_type=None, amount=None):
         """
         Check if account has enough credits.
         
         Args:
             account: Account instance
-            required_credits: Number of credits required
+            required_credits: Number of credits required (legacy parameter)
+            operation_type: Type of operation (new parameter)
+            amount: Optional amount for variable costs (new parameter)
         
         Raises:
             InsufficientCreditsError: If account doesn't have enough credits
         """
+        # Support both old and new API
+        if operation_type:
+            required_credits = CreditService.get_credit_cost(operation_type, amount)
+        elif required_credits is None:
+            raise ValueError("Either required_credits or operation_type must be provided")
+        
         if account.credits < required_credits:
             raise InsufficientCreditsError(
                 f"Insufficient credits. Required: {required_credits}, Available: {account.credits}"
@@ -121,6 +153,9 @@ class CreditService:
         """
         Calculate credits needed for an operation.
         
+        DEPRECATED: Use get_credit_cost() instead.
+        Kept for backward compatibility.
+        
         Args:
             operation_type: Type of operation
             **kwargs: Operation-specific parameters
@@ -131,31 +166,31 @@ class CreditService:
         Raises:
             CreditCalculationError: If calculation fails
         """
-        if operation_type not in CREDIT_COSTS:
-            raise CreditCalculationError(f"Unknown operation type: {operation_type}")
+        # Map old operation types to new ones
+        operation_mapping = {
+            'ideas': 'idea_generation',
+            'content': 'content_generation',
+            'images': 'image_generation',
+            'reparse': 'image_prompt_extraction',
+        }
         
-        cost_config = CREDIT_COSTS[operation_type]
+        mapped_type = operation_mapping.get(operation_type, operation_type)
         
-        if operation_type == 'clustering':
-            # 1 credit per 30 keywords
+        # Handle variable costs
+        if mapped_type == 'content_generation':
+            word_count = kwargs.get('word_count') or kwargs.get('content_count', 1000) * 100
+            return CreditService.get_credit_cost(mapped_type, word_count)
+        elif mapped_type == 'clustering':
             keyword_count = kwargs.get('keyword_count', 0)
-            credits = max(1, int(keyword_count * cost_config['per_keyword']))
-            return credits
-        elif operation_type == 'ideas':
-            # 1 credit per idea
+            # Clustering is fixed cost per request
+            return CreditService.get_credit_cost(mapped_type)
+        elif mapped_type == 'idea_generation':
             idea_count = kwargs.get('idea_count', 1)
-            return cost_config['base'] * idea_count
-        elif operation_type == 'content':
-            # 3 credits per content piece
-            content_count = kwargs.get('content_count', 1)
-            return cost_config['base'] * content_count
-        elif operation_type == 'images':
-            # 1 credit per image
+            # Fixed cost per request
+            return CreditService.get_credit_cost(mapped_type)
+        elif mapped_type == 'image_generation':
             image_count = kwargs.get('image_count', 1)
-            return cost_config['base'] * image_count
-        elif operation_type == 'reparse':
-            # 1 credit per reparse
-            return cost_config['base']
+            return CreditService.get_credit_cost(mapped_type) * image_count
         
-        return cost_config['base']
+        return CreditService.get_credit_cost(mapped_type)
 
diff --git a/backend/igny8_core/modules/system/models.py b/backend/igny8_core/modules/system/models.py
index 219412bc..0ba175ed 100644
--- a/backend/igny8_core/modules/system/models.py
+++ b/backend/igny8_core/modules/system/models.py
@@ -6,7 +6,7 @@ from igny8_core.auth.models import AccountBaseModel
 
 # Import settings models
 from .settings_models import (
-    SystemSettings, AccountSettings, UserSettings, ModuleSettings, AISettings
+    SystemSettings, AccountSettings, UserSettings, ModuleSettings, AccountModuleSettings, AISettings
 )
 
 
diff --git a/backend/igny8_core/modules/system/settings_models.py b/backend/igny8_core/modules/system/settings_models.py
index 075678e7..93c87f8c 100644
--- a/backend/igny8_core/modules/system/settings_models.py
+++ b/backend/igny8_core/modules/system/settings_models.py
@@ -92,6 +92,61 @@ class ModuleSettings(BaseSettings):
         return f"ModuleSetting: {self.module_name} - {self.key}"
 
 
+class AccountModuleSettings(AccountBaseModel):
+    """
+    Account-level module enable/disable settings.
+    Phase 0: Credit System - Module Settings
+    """
+    # Module enable/disable flags
+    planner_enabled = models.BooleanField(default=True, help_text="Enable Planner module")
+    writer_enabled = models.BooleanField(default=True, help_text="Enable Writer module")
+    thinker_enabled = models.BooleanField(default=True, help_text="Enable Thinker module")
+    automation_enabled = models.BooleanField(default=True, help_text="Enable Automation module")
+    site_builder_enabled = models.BooleanField(default=True, help_text="Enable Site Builder module")
+    linker_enabled = models.BooleanField(default=True, help_text="Enable Linker module")
+    optimizer_enabled = models.BooleanField(default=True, help_text="Enable Optimizer module")
+    publisher_enabled = models.BooleanField(default=True, help_text="Enable Publisher module")
+    
+    updated_at = models.DateTimeField(auto_now=True)
+    created_at = models.DateTimeField(auto_now_add=True)
+    
+    class Meta:
+        db_table = 'igny8_account_module_settings'
+        verbose_name = 'Account Module Settings'
+        verbose_name_plural = 'Account Module Settings'
+        # One settings record per account
+        constraints = [
+            models.UniqueConstraint(fields=['account'], name='unique_account_module_settings')
+        ]
+        indexes = [
+            models.Index(fields=['account']),
+        ]
+    
+    def __str__(self):
+        account = getattr(self, 'account', None)
+        return f"ModuleSettings: {account.name if account else 'No Account'}"
+    
+    @classmethod
+    def get_or_create_for_account(cls, account):
+        """Get or create module settings for an account"""
+        settings, created = cls.objects.get_or_create(account=account)
+        return settings
+    
+    def is_module_enabled(self, module_name):
+        """Check if a module is enabled"""
+        module_map = {
+            'planner': self.planner_enabled,
+            'writer': self.writer_enabled,
+            'thinker': self.thinker_enabled,
+            'automation': self.automation_enabled,
+            'site_builder': self.site_builder_enabled,
+            'linker': self.linker_enabled,
+            'optimizer': self.optimizer_enabled,
+            'publisher': self.publisher_enabled,
+        }
+        return module_map.get(module_name, True)  # Default to enabled if module not found
+
+
 # AISettings extends IntegrationSettings (which already exists)
 # We'll create it as a separate model that can reference IntegrationSettings
 class AISettings(AccountBaseModel):
diff --git a/backend/igny8_core/modules/system/settings_serializers.py b/backend/igny8_core/modules/system/settings_serializers.py
index 7bc10e9a..e2c7d484 100644
--- a/backend/igny8_core/modules/system/settings_serializers.py
+++ b/backend/igny8_core/modules/system/settings_serializers.py
@@ -2,7 +2,7 @@
 Serializers for Settings Models
 """
 from rest_framework import serializers
-from .settings_models import SystemSettings, AccountSettings, UserSettings, ModuleSettings, AISettings
+from .settings_models import SystemSettings, AccountSettings, UserSettings, ModuleSettings, AccountModuleSettings, AISettings
 from .validators import validate_settings_schema
 
 
@@ -58,6 +58,18 @@ class ModuleSettingsSerializer(serializers.ModelSerializer):
         return value
 
 
+class AccountModuleSettingsSerializer(serializers.ModelSerializer):
+    """Serializer for Account Module Settings (Phase 0)"""
+    class Meta:
+        model = AccountModuleSettings
+        fields = [
+            'id', 'planner_enabled', 'writer_enabled', 'thinker_enabled',
+            'automation_enabled', 'site_builder_enabled', 'linker_enabled',
+            'optimizer_enabled', 'publisher_enabled', 'created_at', 'updated_at'
+        ]
+        read_only_fields = ['created_at', 'updated_at', 'account']
+
+
 class AISettingsSerializer(serializers.ModelSerializer):
     class Meta:
         model = AISettings
diff --git a/backend/igny8_core/modules/system/settings_views.py b/backend/igny8_core/modules/system/settings_views.py
index 18da126f..a43edcca 100644
--- a/backend/igny8_core/modules/system/settings_views.py
+++ b/backend/igny8_core/modules/system/settings_views.py
@@ -13,10 +13,10 @@ from igny8_core.api.authentication import JWTAuthentication, CSRFExemptSessionAu
 from igny8_core.api.pagination import CustomPageNumberPagination
 from igny8_core.api.throttles import DebugScopedRateThrottle
 from igny8_core.api.permissions import IsAuthenticatedAndActive, HasTenantAccess, IsAdminOrOwner
-from .settings_models import SystemSettings, AccountSettings, UserSettings, ModuleSettings, AISettings
+from .settings_models import SystemSettings, AccountSettings, UserSettings, ModuleSettings, AccountModuleSettings, AISettings
 from .settings_serializers import (
     SystemSettingsSerializer, AccountSettingsSerializer, UserSettingsSerializer,
-    ModuleSettingsSerializer, AISettingsSerializer
+    ModuleSettingsSerializer, AccountModuleSettingsSerializer, AISettingsSerializer
 )
 
 
@@ -276,6 +276,75 @@ class ModuleSettingsViewSet(AccountModelViewSet):
         serializer.save(account=account)
 
 
+@extend_schema_view(
+    list=extend_schema(tags=['System']),
+    retrieve=extend_schema(tags=['System']),
+    update=extend_schema(tags=['System']),
+    partial_update=extend_schema(tags=['System']),
+)
+class AccountModuleSettingsViewSet(AccountModelViewSet):
+    """
+    ViewSet for managing account module enable/disable settings.
+    Phase 0: Credit System - Module Settings
+    One settings record per account (get_or_create pattern)
+    """
+    queryset = AccountModuleSettings.objects.all()
+    serializer_class = AccountModuleSettingsSerializer
+    permission_classes = [IsAuthenticatedAndActive, HasTenantAccess]
+    authentication_classes = [JWTAuthentication, CSRFExemptSessionAuthentication]
+    pagination_class = CustomPageNumberPagination
+    throttle_scope = 'system'
+    throttle_classes = [DebugScopedRateThrottle]
+    
+    def get_queryset(self):
+        """Get module settings for current account"""
+        queryset = super().get_queryset()
+        return queryset.filter(account=self.request.account)
+    
+    def list(self, request, *args, **kwargs):
+        """Get or create module settings for account"""
+        account = request.account
+        settings = AccountModuleSettings.get_or_create_for_account(account)
+        serializer = self.get_serializer(settings)
+        return success_response(data=serializer.data, request=request)
+    
+    def retrieve(self, request, pk=None):
+        """Get module settings for account"""
+        account = request.account
+        try:
+            settings = AccountModuleSettings.objects.get(account=account, pk=pk)
+        except AccountModuleSettings.DoesNotExist:
+            # Create if doesn't exist
+            settings = AccountModuleSettings.get_or_create_for_account(account)
+        serializer = self.get_serializer(settings)
+        return success_response(data=serializer.data, request=request)
+    
+    def perform_create(self, serializer):
+        """Set account automatically"""
+        account = getattr(self.request, 'account', None)
+        if not account:
+            user = getattr(self.request, 'user', None)
+            if user:
+                account = getattr(user, 'account', None)
+        
+        if not account:
+            from rest_framework.exceptions import ValidationError
+            raise ValidationError("Account is required")
+        
+        serializer.save(account=account)
+    
+    @action(detail=False, methods=['get'], url_path='check/(?P<module_name>[^/.]+)', url_name='check_module')
+    def check_module(self, request, module_name=None):
+        """Check if a specific module is enabled"""
+        account = request.account
+        settings = AccountModuleSettings.get_or_create_for_account(account)
+        is_enabled = settings.is_module_enabled(module_name)
+        return success_response(
+            data={'module_name': module_name, 'enabled': is_enabled},
+            request=request
+        )
+
+
 @extend_schema_view(
     list=extend_schema(tags=['System']),
     create=extend_schema(tags=['System']),
diff --git a/backend/igny8_core/modules/system/urls.py b/backend/igny8_core/modules/system/urls.py
index 5e19b49c..3928e133 100644
--- a/backend/igny8_core/modules/system/urls.py
+++ b/backend/igny8_core/modules/system/urls.py
@@ -7,7 +7,7 @@ from .views import AIPromptViewSet, AuthorProfileViewSet, StrategyViewSet, syste
 from .integration_views import IntegrationSettingsViewSet
 from .settings_views import (
     SystemSettingsViewSet, AccountSettingsViewSet, UserSettingsViewSet,
-    ModuleSettingsViewSet, AISettingsViewSet
+    ModuleSettingsViewSet, AccountModuleSettingsViewSet, AISettingsViewSet
 )
 router = DefaultRouter()
 router.register(r'prompts', AIPromptViewSet, basename='prompts')
@@ -17,6 +17,7 @@ router.register(r'settings/system', SystemSettingsViewSet, basename='system-sett
 router.register(r'settings/account', AccountSettingsViewSet, basename='account-settings')
 router.register(r'settings/user', UserSettingsViewSet, basename='user-settings')
 router.register(r'settings/modules', ModuleSettingsViewSet, basename='module-settings')
+router.register(r'settings/account-modules', AccountModuleSettingsViewSet, basename='account-module-settings')
 router.register(r'settings/ai', AISettingsViewSet, basename='ai-settings')
 
 # Custom URL patterns for integration settings - matching reference plugin structure