The Free SaaS Stack Guide — A Real Business on $0/Month

You don't need seed funding to launch a real SaaS. You need a stack.

We've shipped production apps — actual paying customers, actual uptime — on $0 a month in infrastructure costs. Not a demo. Not a hobby project. Real businesses, running on stacked free tiers, with headroom to grow before a single dollar hits a card.

Here's the full walkthrough.

Start with the edge. Cloudflare is the layer everything else sits on top of. DNS, CDN, DDoS protection, SSL — all free, all unlimited. You point your domain at Cloudflare, you get a global edge network for the cost of the domain itself. Most SaaS founders don't realize how much infrastructure Cloudflare gives away. Pages hosting, Workers for serverless functions, R2 for object storage with no egress fees, KV for edge key-value, D1 for SQLite at the edge. You could build a real app on Cloudflare alone and never leave the free tier until you're shipping millions of requests a month.

Auth next. Clerk handles sign-in, sign-up, social logins, MFA, session management, and user metadata up to 10,000 monthly active users on the free tier. That's not a demo cap — that's a real MAU count. If you've got 10,000 active users and still haven't started charging, the problem isn't Clerk's pricing. The integration takes about twelve minutes. Drop in their middleware, wire up the sign-in page, done. You just replaced what used to be a six-week engineering project.

Data layer. Airtable for structured user data, content, and anything that looks like a spreadsheet. Free tier is 1,000 records per base, which sounds small until you realize you can run multiple bases and federate them. For anything that needs a real relational database, Turso gives you SQLite replicated globally with a generous free tier — 500 databases, 9GB of storage, a billion row reads a month. That's not a typo. A billion.

"Axiom for logs, 500GB a month free, which is frankly absurd for a free tier."

For a hot cache and rate limiting, Upstash Redis. Serverless Redis, free up to 10,000 commands per day, pay-as-you-go after. The free tier carries you through early beta and most of your first hundred users without a charge.

Email. Resend. 100 emails a day free, 3,000 a month. Transactional email, welcome flows, password resets, receipts. Their deliverability is genuinely good because they're built by the Postmark team. API is three lines. Templates are React components. No ESP migration dance, no SMTP fiddling.

Payments. Stripe. Obviously. Stripe isn't technically free — they take a cut per transaction — but there's no monthly minimum, no setup fee, no SaaS subscription. You only pay when you make money, which is the correct shape of a payment processor's pricing. Stripe Checkout gives you hosted pages. Stripe Billing handles subscriptions. Stripe Customer Portal gives users self-serve upgrade and cancel. You ship a billing system in a day.

Observability. Axiom for logs, 500GB a month free, which is frankly absurd for a free tier. Sentry for errors, 5,000 events a month free. Betterstack for uptime monitoring on the free tier. You get production-grade observability on three separate services for zero dollars. The stack most Series A companies run is not materially better than what you can cobble together free.

Hosting. Vercel for the Next.js frontend. Hobby tier is free and carries small SaaS workloads easily. Once you start getting traffic you'll want Pro, but Pro kicks in around real user counts, not before.

LLMs. This is where "free" gets fuzzy. You can run inference free via Vercel AI Gateway credits, Google AI Studio quotas, and Anthropic's Claude API free tier for small volumes. For production, most founders need a budget here — but it's pay-per-use, not a subscription, and you only spend when a user triggers an action. Start with a small credit balance, instrument it, and watch the burn rate.

Here's the pattern when you wire it all together. A user hits your Vercel-hosted Next.js app through Cloudflare DNS. Clerk authenticates them. Their session data lives in Upstash. Their content lives in Turso. Their profile and metadata live in Airtable. When they pay, Stripe fires a webhook that updates their plan in Turso. Resend sends the receipt. Axiom logs every request. Sentry catches every error. If anything breaks, Betterstack pings your phone.

Total monthly cost: $0.

That's not theoretical. That's the actual stack we've used to launch three products in the last year. You can build a real business on this before you spend a single dollar on infrastructure, which means your runway is measured in how long you can pay your own rent, not how long the AWS bill will tolerate you.

The mindset shift is the point. Stop asking "how do I afford to build this" and start asking "what's the free tier for each layer." Almost every category has a generous enough free tier that an early-stage founder can ship production-quality infrastructure without a budget.

Action step: sign up for Cloudflare, Clerk, Turso, Upstash, Resend, Stripe, and Vercel today, then connect a domain and wire the first auth flow. Total time: an afternoon.

See /free-saas-guide for the $0/month stack walkthrough.