Day 1 of validating ProofSent: 5 paying users or kill it

I'm running a strict lean validation sprint.

The problem: Freelancers have no proof that clients reviewed and approved their deliverables. "I never approved that" is one of the most common and costly disputes in freelance work.

The product: ProofSent — send the client a single link, they review your deliverable in browser (no account needed), click Approve, you get a timestamped PDF certificate with their IP. No client login. Works for any file type.

The rule: 5 paying customers (real money, real strangers) within 2 weeks, or I stop and move on.

Landing page is live at proofsent.com. Currently collecting waitlist signups.

Has anyone else run strict kill-it validation sprints like this? What worked for getting those first 5?