About a month after we started Y Combinator we came up with the phrase that became our motto: Make something people want. We've learned a lot since then, but if I were choosing now that's still the one I'd pick.
Another thing we tell founders is not to worry too much about the business model, at least at first. Not because making money is unimportant, but because it's so much easier than building something great.
A couple weeks ago I realized that if you put those two ideas together, you get something surprising. Make something people want. Don't worry too much about making money. What you've got is a description of a charity.
When you get an unexpected result like this, it could either be a bug or a new discovery. Either businesses aren't supposed to be like charities, and we've proven by reductio ad absurdum that one or both of the principles we began with is false. Or we have a new idea.[1]
It's fine to disagree with that advice of course. But I think in the context of YC it make sense. If you aren't doing YC and can't raise capital as easily then maybe not.