Lets see - you missed doing one teensy weensie little thing but you did everything else just great so for this small mistake you feel you should pay some of the $15,000. This little mistake cost the owner $15,000 so sorry you owe for the whole thing. You are a typical PM who wants to do nothing and get paid for doing it and not be liable for their blunders. You don't sound new to this so this mistake was pure and simple gross negligence. Besides - why would you not run credit checks on college students or their parents if they are co-signing? You're poor PM skills caught up to you big time. If you don't pay I hope the owner takes you to court.