Synthetic Multifamily Appraisal Generator

A fully automated system that generates synthetic multifamily loan appraisal packages using AI. Enter a property address and basic details, and the system produces a complete appraisal report (DOCX), rent rolls, and T-12 operating statements.

Architecture

Frontend (React/Vercel)
    │
    ▼
API Gateway ──► Input Validator Lambda
                    │
                    ▼
              Step Functions Orchestrator
                    │
                    ▼
              Crosswalk Generator (Haiku)
              ─── generates master data schema ───
                    │
        ┌───────────┼───────────────┐
        ▼           ▼               ▼
  Section 1-12   T-12/Rent Roll   Image Gen
  (Haiku/Sonnet/  (Sonnet +       (Haiku +
   Opus)          openpyxl)       Replicate)
        └───────────┼───────────────┘
                    ▼
              QC Validator (Sonnet)
                    │
                    ▼
              Document Assembler (Pandoc)
                    │
                    ▼
              S3 ──► Presigned Download URLs

Tech Stack

Layer	Technology
Frontend	React 18 + TypeScript + Tailwind CSS (Vercel)
API	AWS API Gateway (REST)
Orchestration	AWS Step Functions
Compute	AWS Lambda (Python 3.11)
AI Models	AWS Bedrock (Claude Haiku, Sonnet 4.5, Opus 4.6)
Images	Replicate API (z-image-turbo)
Storage	Amazon S3
Notifications	Amazon SNS
IaC	AWS CDK v2 (Python)
Documents	Pandoc, python-docx, openpyxl

Quick Start

Prerequisites

• Python 3.11+
• Node.js 18+
• AWS CLI configured with appropriate credentials
• AWS CDK CLI (npm install -g aws-cdk)
• Pandoc installed
• Replicate API token

Setup

# Clone and install Python dependencies
pip install -r requirements.txt

# Install frontend dependencies
cd frontend && npm install && cd ..

# Copy and fill in environment variables
cp .env.example .env
# Edit .env with your values

Deploy Backend

# Bootstrap CDK (first time only)
cdk bootstrap

# Deploy all stacks
cdk deploy --all

Deploy Frontend

cd frontend
cp .env.example .env.local
# Set VITE_API_URL to your API Gateway URL
npm run build
vercel --prod

Project Structure

mf_data_gen/
├── cdk/                          # AWS CDK infrastructure
│   ├── app.py                    # CDK app entry point
│   └── stacks/
│       ├── storage_stack.py      # S3, SNS
│       ├── lambda_stack.py       # All Lambda functions
│       ├── stepfunctions_stack.py # Step Functions state machine
│       └── api_stack.py          # API Gateway
├── lambdas/
│   ├── shared/                   # Shared utilities
│   │   ├── models.py             # Pydantic crosswalk schema
│   │   ├── bedrock_client.py     # Bedrock API client
│   │   ├── s3_utils.py           # S3 read/write helpers
│   │   └── section_generator.py  # Base class for sections
│   ├── input_validator/          # Validates user input
│   ├── crosswalk_generator/      # Generates master data (CRITICAL)
│   ├── section_generators/       # 12 appraisal sections
│   │   ├── section_01/ (Haiku)   # Introduction
│   │   ├── section_02/ (Sonnet)  # Property Description
│   │   ├── section_03/ (Sonnet)  # Market Analysis
│   │   ├── section_04/ (Haiku)   # Highest and Best Use
│   │   ├── section_05/ (Haiku)   # Valuation Methodology
│   │   ├── section_06/ (Opus)    # Sales Comparison
│   │   ├── section_07/ (Opus)    # Income Approach
│   │   ├── section_08/ (Haiku)   # Cost Approach
│   │   ├── section_09/ (Opus)    # Reconciliation
│   │   ├── section_10/ (Haiku)   # Assumptions
│   │   ├── section_11/ (Haiku)   # Certification
│   │   └── section_12/ (Haiku)   # Addenda
│   ├── image_generator/          # Replicate image generation
│   ├── t12_generator/            # Excel T-12 and rent roll
│   ├── qc_validator/             # Data consistency checks
│   ├── assembler/                # DOCX assembly + ZIP
│   ├── status_checker/           # Job status API
│   └── download_handler/         # Presigned URL API
├── frontend/                     # React SPA
├── templates/                    # Markdown templates
├── tests/                        # pytest test suite
├── scripts/                      # Deploy scripts
└── docs/                         # Documentation

API Endpoints

Method	Path	Description
POST	/api/generate	Start appraisal generation
GET	/api/status/{job_id}	Check generation progress
GET	/api/download/{job_id}	Get download URLs

Configuration

Variable	Description
AWS_ACCOUNT_ID	AWS account ID
AWS_REGION	AWS region (default: us-east-1)
REPLICATE_API_TOKEN	Replicate API key for image generation
S3_BUCKET	S3 bucket name

Testing

pytest tests/ -v