“I tell founders to spend months working with a potential co-founder before you sign anything, because the wrong co-founder is worse than none at all. Test the hard stuff up front: who is CEO, how long each of you can go without pay, and what happens when you disagree on a pivot.”
“The fastest way to test a potential co-founder is to commit to one person and one idea, then see if you both keep choosing each other when it gets hard. At EF we celebrate breakups because discovering fast that it is not working is the most respectful and efficient outcome.”
“I spent months talking with Amy before we started Outcast, not about decks, but about who holds final say, what we look like at our worst, and what would make us resent each other. Most founders skip this because it feels awkward, but a co-founder is a decade-long bet, and the hard conversations are the diligence.”
“I watch how they handle a real working sprint, not a coffee chat. Alice Bentinck at Entrepreneur First put 30 to 50 candidates through hackathon-style tests because you cannot predict fit from a resume; I saw the same thing building my own founding teams. The right co-founder makes you more productive under pressure, not less.”
“I would vet a potential cofounder the same way I pressure-test a founding team before a big SBIR push: look past credentials and watch how they behave when things get hard. In my first startup, I had four chemistry PhDs as cofounders. We were all technically strong, but we were too similar, and we avoided the hard conversations about equity, roles, and expectations early on.”
“I would make them prove they can handle conflict before you ever sign anything. Work together informally on a real problem for a month, then have a hard disagreement and see how it lands.”
“I’ve watched dozens of co-founder relationships crash, and 99% of the time the wreck was avoidable. The vetting that matters isn’t skill overlap; it’s whether you share the same definition of success, the same values, and the same tolerance for the grind.”
“I have watched too many founders fall in love with a cofounder's résumé and skip the real test. I make them work on something small and hard together for a few weeks, because how someone behaves when the product breaks and the customer is angry tells you everything the interview cannot.”
“I look for the same thing in a cofounder that I look for as an investor: can we actually argue well together and still want to keep going. With Philip, we built two companies over twenty years because we learned to be honest without being destructive, and that is rarer than a great idea or a perfect cap table.”