No. Just because they got into YC doesn't mean you should work for rent. They haven't made it, they've still got a significant chance of failing, and you work

No. Just because they got into YC doesn't mean you should work for rent. They haven't made it, they've still got a significant chance of failing, and you working there is going to directly impact whether or not they do make it so you should be rewarded beyond "living expenses". If they can't appreciate that then bugger them. I can't help but feel there's no way they couldn't appreciate how significant a third set of hands would be and you shouldn't work for them anyway because there is something rotten there.