A week before Closing on our house the seller backs out! What can I do? What about the fee's (inspection etc?

I live in Omaha Nebraska and was planning to purchase our first home here. We had everything ready to Close in a week and the buyer looses her job and backed out! Here i am with a pregnant wife and five year old!!! And out apx $1500. We stipulated that we would not sign off on the house until paid,but how long can that be? What can I do?