Build a SaaS MVP With AI (The Capstone: Auth + Data + Payments + Launch)

SaaS is the business model everyone circles: build once, charge monthly. Here's the demystification — a SaaS MVP is five components you've already built if you've worked through this site: a landing page (waitlist tutorial), accounts (auth tutorial), a core feature on per-user data (any app tutorial + RLS), payments (Stripe tutorial), and the safety pass (security guide). What's new is assembly order, scope discipline, and project size. This tutorial is the assembly manual.

Step 0 — The two gates

Gate one: validation. If you haven't run the landing-page-waitlist experiment and gotten a signal, stop — building the product first is the expensive way to learn nobody wants it. Gate two: scope. Write the sentence 'Users pay me $X/month to ____' with ONE thing in the blank. Your MVP is that blank plus login plus billing. Every 'and also' you resist now is a week you get back.

Step 1 — Set up like a project, not a chat

At this size, the single-file-per-conversation workflow breaks down. Graduate to the Claude Code pattern (its tutorial is the on-ramp): one project folder, a CLAUDE.md stating the stack and rules ('Supabase for auth+data, vanilla JS, every table gets RLS at creation, no frameworks'), and files the agent maintains across sessions. Then have it scaffold: landing page, /app (the product), /account, the Supabase schema. The spec-extraction prompt from the prompt-patterns guide becomes your save-game between weekends — use it religiously.

Step 2 — Build the feature BEFORE the billing

Weekend one ships: signup → log in → use the one feature → data persists per-user (auth tutorial's isolation test, always). No payments yet — get five waitlist people using it FREE first. Their confusion is your bug list; their 'oh nice, but could it…' is your roadmap; their silence is gate one reopening. A week of free users routinely saves a month of building the wrong polish.

Step 3 — Billing, the honest-MVP way

Step 4 — The pre-launch trinity

(1) Security: the AI-code-safety review, full Tier-3 paranoia — you now hold strangers' data AND money. (2) Legal basics: terms of service, privacy policy, refund policy — AI drafts them honestly stated, your jurisdiction named; for an MVP this is diligence, for growth it's a lawyer's hour. (3) Operational floor: Supabase backups confirmed on, your error states human-readable, a support email that you actually check, and Stripe spending alerts. None of this is glamorous; all of it is what 'real product' means.

Step 5 — Launch means emailing the waitlist

Not a launch platform splash — your waitlist, personally: here's the thing you asked for, here's founder pricing, reply with anything. A 30-person waitlist converting 3 paying customers is a SPECTACULAR start: real revenue, real users, real feedback loop. Then the operating rhythm: ship one improvement weekly (announced to users — momentum is retention), watch where people stop using it more than what they request, and run the security prompt at every new power, forever.

The honest scoreboard

Most MVPs don't become businesses — usually for demand reasons no code quality fixes, which is why the gates exist. But the downside case here is: you spent ~$50 and some weekends, you now hold the full stack (auth, data, payments, webhooks, operations) as proven personal capability, and the next idea costs half as much to test. The people with five 'failed' MVPs and one working SaaS aren't unlucky-then-lucky; that's just what the process looks like from inside. This site's whole catalog was the training montage — this project is the fight.