Grace, I had a long, well thought out answer to your question and went to look at community guidelines link above and returned to find my answer gone.
I'll try again--if what you are hoping to accomplish is a short sale, having an experienced professional on your side may be essential. Not to say that you can't get it done, but the short sale process can be a minefield for someone with no experience at it. First and foremost is that the seller has to have faced the reality of being upside down in their house. Their best case scenario may be walking with dented credit and no cash, rather than trashed credit and no cash. If they haven't "gotten religion" on that issue, you are facing an uphill battle and a real estate professional with experience in this arena can be extremely valuable.
In order to do a short sale, the banks will require a complete short sale package, which involves financial and personal info from the seller, so his/her cooperation and emotional buy-in is essential to the process.
email me if you want a list of what's involved: email@example.com
I would suggest using local print (newspapers, real estate book, etc) ads to locate a Realtor who does deal with short sales. A broker who has homes advertised as short sale candidates is likely to have some experience in them. I would not use the internet for this particular search, as "short people" (check this post for one broker's experience with and warning about what he calls "short people" http://activerain.com/blogsview/640002/I-ll-Have-a
will turn up and are to be avoided! Don't hire a broker that uses them either!
A couple of warnings--be prepared to be very patient--whether you go it alone or hire a buyer's agent.
Short sales are rarely good opportunities for anyone on a tight time frame, that needs to be into a house on a deadline. The Loss Mitigation folks at the bank involved won't consider a short sale without a COMPLETE package and then their first step is going to be to get an appraisal or BPOs (broker's price opinion) from local agents. It is likely you won't hear from them before this is complete. Inexplicably, this can take weeks, or in some cases longer. Patience is not just a virtue in short sales, it is a necessity.
Another suggestion--Realty Trak is reasonably reliable but they don't always have the most up to date info. The property owner you have identified may have already sold his/her home, or may have come up with a solution such as a refi or other financial workout to satisfy the lender, or may have filed bankruptcy protecting their home in the process. If your county has their land records on line, learn to use them.