The short answer is that there are no guarantees.  Certainly, it will take more than the usual 30 days since the seller's lender must approve the discounted payoff before a closing can occur.  The best we can do is give you an educated guess based on the circumstances of that particular offer.  The lender can be the reason for delays up to 90 days.  The LARGEST SERVICER whose initials are CW, will probably take the longest.  Their process is extremely inefficient so patience will definitely need to be a virtue the buyers possess.  Lately, it can take as long as 90 days from contract to close. 

Another mitigating factor which may delay the process is the amount of the offer.  If it is too low, the lender may not even consider the short sale offer at all since many of them now have "in house" appraisals.  That concept is interesting to me since all markets are subjective based on location and the people who are doing these "in house" appraisals are not appraisers or realtors.  I believe it is a concept they will abandon in short order once they see how much time they end up spending fighting with REAL appraisers and realtors over differing opinions as to value.

Most importantly, just remember, as a buyer, seller or agent, everyone has to be IN IT TO WIN IT in order to get the GREAT DEAL!!