The answer to that is don't, get somebody to go and look at it. You might be buying a money pit, you could be looking at upwards of $10,000 for covering/engine/prop/instruments. 360 hours of unmaintained time is enough to stuff an Airframe, why did he decide to scrap the Aircraft? I would not spend even $900 on something unseen. If you keen you'd have to go and pick it up anyway so take your money and somebody who knows what to look for, if all's well then grab it.
The thing is not to look at it stary eyed, for the money it could cost to rebuild you could buy something flying in good nick. There are some good deals around at the moment, Thrusters with 582's in good condition for $15,000, you could easily spend that rebuilding and 800 hours of your time doing it.
On the other hand IF (that's a big IF) the Airframe is in good condition and you have a very limited budget, you could get the thing flying with lots of your time and a second hand 503, some access to knowledgable help for maybe $5,000.