The above is true in a majority of situations where you have no formal contract with the roommate and it's just basically a cost sharing arraignment. Example:
You are renting your apt and you are the one who signed the lease. A friend moves in with you and pays half the rent. There is NO formal, enforceable rental agreement between you and the roommate. Its' just a cost sharing arraignment is all. The room mate pays half the rent, you pay the other half. Nothing is official, in writing or recorded anywhere. The room mate has no legal oblication to *your* landlord to pay jack squat. In this case, the roommate is giving you a gift of half the rent every month, so *you* are maintaining the household. If you signed the lease, you are the only one obligated to pay anyway.
Now if you're in a state that offers a renter's credit, more than likely your room mate wants their cut of that credit, if they're helping pay rent. That would call for a formal, legally enforceable rental agreement between you and the roommate if *YOU* are the one renting out space that *YOU* do not own and pay rent for. (Most rental agreements explicitly do not allow you to sub-let) In this case, you are collecting the rent as a landlord, and you are responsible for "maintaining the household" in it's entirety, since as a landlord you are responsible for the real estate being rented by your roommate. (If the rental agreement is with you, then *YOU* are the responsible party, not the land lord you pay as *your* landlord has no agreement or legal obligations to your roommate tenant) In this case, the rent you receive from the tenant (and report as income on your tax return of course!) is "YOUR" money now. So when you pay *you* landlord, it's *you* that is paying 100% of the rent that *you* are legally obligated to pay.
It's all semantics and matters how you set things up, as well as the wording in all rental agreement/contracts.
