We make the first client project free. How do we prove it's not a scam?

Small eng shop here. We ship production software in a fixed 14-day window — senior engineers + AI for the boilerplate, code in the client's GitHub from hour one. The first project is free; paid work after runs on Stripe milestone escrow.

The logic: a free first build is a cheaper, faster audition than any pilot or procurement cycle. Hate the result? Keep the code and walk. Like it? We're already running.

The problem: serious buyers hear "free" and think bait-and-switch or junior offshore team. Saying it isn't doesn't kill the doubt — showing it has to.

So: what would actually make you trust a "first one's free" dev shop? A public sample repo? Named team? Something else?