Keep in mind that the short sale is a bit of a crapshoot. Lenders might reject your short sale application for any reason or no reason at all. Other property proposals may take priority, the price may be too low or the wrong person may go on vacation at the wrong time.
When your application is submitted, you may have a bit of a wait until you hear whether or not your proposal is approved. Once you get the call that your bid is accepted, though, you need to jump into action and make sure you'll be financially prepared in time for the closing.
Many banks will give you 30 days to get your financing together, but some won't give you nearly that. You need to be prepared in case that deadline is sooner rather than later. So if you don't have the full amount in cash on hand, then try to get qualified for the loan before the short sale approval actually comes through. This way you have a better chance of meeting tight sale deadlines.