Disclaimer: I don't live in Silicon Valley, and I've never worked at a startup, but this seems really shady/dishonest. First of all, 15% equity sounds like very

Disclaimer: I don't live in Silicon Valley, and I've never worked at a startup, but this seems really shady/dishonest. First of all, 15% equity sounds like very little for a co-founder unless you're only putting 15% of the work in. Second of all, this idea of wanting the "loan" back should have come up during the equity split discussions. Otherwise, he's essentially lied to you about the nature of the "investment". Have a conversation about this with the co-founder right away.