The problem with living with people where the boundaries are fuzzy: friends, situationships, partners - is once money is involved now you treat them differently then you would a stranger, so you become responsible for their problems. The implied threat is if you hold them responsible you lose the social relationship. If a stranger was living in your house and can't make rent, what would you do? What would your landlord do if you couldn't make rent? I think the healthiest thing is to not see yourself as a buffer for your friends problems, but a middleman for their obligation to the landlord/rent burden. If they don't make rent, be sympathetic, be heartfelt, but they have to move out so rent can be made. If this friend wasnt living with you, and wanted to borrow money but if you lent it to them you wouldnt be able to pay your own rent... Would you do it?

It's a topic that often comes up when people vent. People feel better after they talk about their problems. Hence it feels good to get it off their chest.