We are sponsoring a kid who is 22 (wife's nephew).  He has a student
visa and cannot work except at school and for minimum wage.  We signed
an agreement stating that we will provide a roof, food and proof that
we have enough money to support him.  He is gobbling up credit cards
and using them for discretionary spending against our advice.  Once he
leaves are we liable for his debts?  I have not co-signed and as far
as I know my wife has not either and he again is 22.