I Built a Full SaaS Finance App Solo Using AI — Here's My Honest Take on Every Model I Used

I'm a DevOps engineer. Not a "real" fullstack developer by training. But over the past year I've been building YourFinanceWORKS — a self-hosted, AI-powered finance platform with invoicing, OCR receipt processing, bank reconciliation, multi-tenant architecture, MCP integration, and a full business intelligence layer. Python/FastAPI backend. React + TypeScript + Vite frontend. 670+ commits. One person. AI made this possible. And I went through a lot of models to get here. This is my honest, unsponsored breakdown of every model I used — what worked, what didn't, and what surprised me. 🧪 Phase 1: The Free Model Rotation Before paying for anything, I treated free models like a buffet. Here's what I found: Windsurf SWE-1.5 Genuinely the best free option for coding tasks. Fast responses, decent output quality, and it handles real engineering problems — not just toy examples. I've half-jokingly wondered if Windsurf has some Google collaboration going on given how polished it feels for a free t