I built a SaaS in a week with Next.js, Supabase, and Stripe — here's what I learned

Last week I went from idea to deployed SaaS in about a week of evening sessions. Here's the product, the stack, and what I learned. The product: RentView — a rental property profit tracker for landlords with 1-10 units. It tracks income, expenses, and net cash flow per property per month. No bank integrations, no tenant management, no bloat. Just "is this property making money?" The stack: Next.js 14 (App Router) for the frontend and API routes Supabase for auth, database (Postgres), and row-level security Stripe for subscriptions ($9/29/49 per month) Vercel for hosting Tailwind CSS for styling Pure SVG for charts (no recharts or Chart.js) Key decisions: Supabase RLS means all security is at the database level — users can only query their own data regardless of what the frontend does No chart library — SVG bar charts and line charts are ~50 lines of code each and add zero bundle size Mortgage auto-calculates as a monthly expense so users don't have to log it every month 7-day free tria