How I Built a Rental Property Deal Analyzer with FastAPI and AI

I spent months evaluating rental properties with spreadsheets and paid calculator subscriptions before deciding to build my own tool. The result is a free, open-source web app that calculates 20+ investment metrics, scores deals on a 14-point system, projects 5-year returns, and runs optional AI analysis -- all from two files with zero build step. Live demo: https://rental-property-deal-analyzer.onrender.com GitHub: https://github.com/berkcankapusuzoglu/Rental-Property-Deal-Analyzer The Problem If you are evaluating rental property investments, you need answers to basic questions: What is the cash-on-cash return? Does it pass the 1% rule? What is the DSCR? What is the total return over 5 years when you factor in appreciation, debt paydown, and tax benefits? Paid tools like DealCheck charge $10-20/month. Spreadsheets are fragile and tedious. I wanted something that was fast, thorough, and free. The Solution A 6-step wizard that walks you through property info, financing, income, expense