If you have been pre-qualified by a bank and they are willing to give you the loan with 5% down you should not have a problem. Just keep in mind that a "short sale is subject to third party approval. The third party is the bank that holds the current owners mortgage. If the third party does not approve the sale the deal will falter regardless of how much you are putting down. Often times you can offer the full asking price and it may still be declined.
If you want to find out more about short sales do some research on Google or contact me and I can explain to you further how they work along with the pros and cons of a short sale deal. Either way, good luck!
Mitchell S. Feldman
Associate Broker/ Director of Sales
Madison Estates & Properties, Inc.
Office: (718) 645-1665/ Cell: (917) 805-0783