A short sale can come about for many different reasons. In my wife's case, she was the owner of the house and had been making payments. We bought an investment property and put it solely in her name to protect our family in the event that the market took a turn for the worse. It did. We owed 590k, but the best offer we had after 6 months was 550k. The short sale prevented her from having to file bankruptcy, and there was no derogatory credit reporting because there were no late payments made.
Despite popular belief, YOU DO NOT HAVE TO BE BEHIND ON YOUR MORTGAGE TO REQUEST A SHORT SALE. You just have to demonstrate that your house can't be sold for what you owe.
In other cases, short sales happen when a seller can't afford to make their payments and is nearing foreclosure or bankruptcy. It makes life much more complicated if you are living in the house in question. The bank's ability to scare you is much greater in that case. In this case, a short sale is only slightly better than the alternatives. You will still lose your house, and your credit is still destroyed just because you've made 4-5 late payments on your mortgage.
Despite popular belief, A BANKTUPCY, FORECLOSURE, OR REPOSSESSION DO NOT HURT YOUR CREDIT AS MUCH AS THE MULTITUDE OF LATE PAYMENTS THAT OFTEN LEAD UP TO THEM!!!!! I just cannot stress this enough. People think that a bankruptcy damages their credit beyond repair in and of its own accord. I've had many clients file bankruptcy with 750 scores and no late payments only to have their score drop to 680. It's the clients with 20+ late payments that are having their credit hurt.
Once this huge packet of information is submitted to the lender, you will most likely hear back in 1-4 weeks on the TERMS of their "approval."