In my experience, having a number of short sale listings did not improve my chances of getting listings....just the opposite, as a matter of fact. Homes I had listed as short sales, if not sold, ALWAYS were listed with other brokers. (This was from my work with Titanium Solutions). I discussed this with a couple people in the loss mit depts of lenders and was told they didn't think the short sale listing broker would work as hard to sell the property if they knew they would get it as an REO. They considered it kind of a conflict of interest. I took great exception to this philosophy, but was never able to get anyone to change their minds.
If you want to get into short sales, I recommend signing up with Titanium. (There is another thread about this company). I know alot of people don't like them, but I have been able to get a lot of listings through them. It takes patience and understanding to do a short sale...I agree! Just my 2 cents.