I understand that Ycombinator works to help non-profit startups - but how does the relationship between investors differ in a non-profit vs a traditional for-profit company?
Err... I think they don't. Not sure they're investors, either, but 'benefactors', contributors, donors or something else. When you give money to a non-profit, I think you're doing so under the assumption that they're not going to give it back, plus a nice return.