Ever clicked a “build an AI SaaS” tutorial and immediately got hit with the infrastructure tax—credit card, five subscriptions, a pile of API keys, S3 for storage, a database for metadata, and a separate backend just to keep the lights on? In this video, I show you how to skip all of that and still ship a production-grade full-stack AI app completely free. We build Roomify: an AI-powered architectural visualization platform that turns 2D floor plans into photorealistic top-down 3D renders using powerful models (from Claude to Gemini) without you managing API keys or paying for servers. I walk you through a modern 2026-ready stack: React + TypeScript (via Vite + React Router v7), Tailwind for fast styling, and Puter.js for the “backend” layer—serverless workers, permanent file hosting, KV storage, and auth using a user-pays model so the app can scale from 1 to 1,000,000 users while you pay nothing. We implement real authentication, set up reusable UI patterns (including generating a Button component with Junie), and establish a workflow to move fast without breaking things by using CodeRabbit for AI code reviews. By the end, you’re not just copying code—you’re learning how to engineer a lightweight, instant, self-contained AI SaaS.