He isn't actually 'on the hook' for anything, legally. Right now she has the teen mom money, so that is what is used for her income in any child support calculations. That said, once the cameras go away he will be on the hook to supply Leah's part of the costs since she isn't working by choice. And, of course, a trip to Disney world (etc.) on a credit card in his name makes him responsible since he took on the debt willingly.