When buying a short sale, the first thing to understand is that it usually takes a while. The hardest part is getting an answer from the bank (hopefully your only dealing with one). This process can take months and it seems like the bank is in no hurry. This is where it seems most short sales fall apart as the buyer gets tired of waiting. The reason for the delay is for every short sale package being submitted a case of fraud has to be open by the bank. Once the offer finally gets accepted, it will usually take less than 30days.
If dealing with two different banks from a 1st and 2nd mortgage this has the potential of being a real nightmare. The problem usually starts when the bank with the 1st mortgage has a policy that states it only will give the bank with the 2nd mortgage a certain amount no matter what the price. The bank with the 2nd mortgage has a policy that states it needs so much on every dollar that is owed. Which in most cases is a lot more than the 1st wants to give to the 2nd. With a lot of luck even this obstacle and be cleared (sometimes).