triple $ landlord liability
Many States penalize Landlords 3 times the original amount on the $Deposit money if they do not refund the money promptly. In small claims court you may be awarded for several times each months rent you stay there past your 30 day 'written' notice.
You might casually tell your landlord about triple landlord liability.
btw Making tenants liable for a landlord's apartment is just corrupt law. Risk is an owner's reponsibility. I hate leases.
My 2 cents is this. Since you signed no contract you are liable for nothing. Your friend did however sign a lease, not month to month, since you stated begin and end dates. Since friend is not tenant, it is up to a small claims judge, but he is probably reponsible. eg Parents sometimes sign leases for their college teen so it's still binding.
Basic Contract: 1) Signer 2) Signee 3) Term 4) Payment 5) Agreement/Responsibilities
Term is begin & end date eg lease eg 1 year OR month to month eg 30 day.
Payment is monthy $ amount, weekly yearly etc.
BTW -- I still want to know how easy leases can be broken under job change. Hmm...