You owe me

A trip to New York with friends: everyone pays for everyone, and by the last day nobody knows who owes who what. The apps we found either cost money or buried the free tier under ads and waiting. That annoyed me enough to want to build it properly: a free, clean way to settle up with friends.

I started it with a co-founder, and before the app really existed we found out we worked badly together. So I made the call early and quit while quitting was still cheap. It is the fastest lesson I have ever collected: who you build with decides more than what you build. I would much rather have learned that on a settle-up app than on something that matters.