 Yeah, so this is a common problem that people get confused on. If you have a lease agreement that is renting the entire property to multiple people, everybody is 100% responsible for the total rent to be paid. So if you have a side agreement with your roommate, hey, I pay half, you pay half, and they don't pay half, you still have to pay the full amount to the landlord. Unless it's a situation where it's rent by room, that is different, but most leases are not like that.