If it works out, you're going to be working on this for 10 years.
Firing people is one of the worst parts of running a company. Actually in my own experience, I think it is the worst.
The track record for founders that don't already know each other is really bad.
The best people know that they should join a rocketship.
A board member of mine used to say sales fix everything in a startup, and that is really true.
In YC's case, the number one cause of early death for startups is cofounder blowups.