Why work evidence matters more than promises
Before two people commit to building something together, each one wants a reasonable answer to a simple question: can this person actually do the work, and will they keep doing it?
Talk is cheap, and everyone is charming in a first video call.
What separates a serious co-founder candidate from an enthusiastic stranger is evidence of real work.
This guide explains what to show a prospective co-founder before you both commit, and what to ask to see from them.
A co-founder relationship is closer to a marriage than a hire.
Y Combinator makes this comparison directly: like a romantic partner, a co-founder is someone you will depend on and spend a great deal of time with, hopefully for many years.
Their advice to matched founders is to work together on a time-boxed trial project with clear expectations and goals before committing Y Combinator on co-founder matching.
That framing has a practical consequence.
If you would not marry someone after one date, you should not merge your ambitions with someone after one conversation.
Evidence, not enthusiasm, is what lets both sides judge compatibility.
Evidence comes in two broad forms: things you have already built, and things you build together on a small scale before committing.
What to show: your existing proof of work
Start with what you already have.
You do not need a finished company or a polished product.
You need artifacts that show how you think, what you finish, and how you work with others.
Work samples and finished artifacts
Show the actual thing, not a description of the thing.
Depending on your field, that might be:
- A working prototype, even an ugly one, that demonstrates the core idea.
- A written analysis, plan, or research memo that shows how you break down a problem.
- Design files, landing pages, scripts, datasets, or customer notes from a past project.
- A volunteer or community project you carried through to completion.
The strongest samples are ones you can walk through end to end: what you set out to do, what you actually did, what went wrong, and what you changed.