I scooped up a "valid" PR5 domain once after a drop, showed "valid" with the site I used, turned out to be a redirect to a popular blog. Cheap, but very valuable lesson for 8 dollars. In my opinion if you buy a dropped or whatever,,, PR domain you should do a check on
http://www.seologs.com/pr-check/pagerank.html for a good PR check first, and then
http://www.archive.org and see if you can continue what the draw was at the domain/site you are interested in rich from

Good Luck
btw, I am not affiliated with either site, I have just found them very useful.