I mean after the contract I have to give $500 to the bank to show I am serious according to the agent. If the short sale procedure take too long, can I void the contract and get my $500 back?
You need to ask your attorney the question, unfortunately Realtor's Code of Ethics prohibit one from advising clients who are already represented and involved in a transaction--refer the question to the agent--but again, your attorney can best advise.