Yup, but that bike on a stand and try and rock the swing arm from side-to-side/up-and-down. Check the bottom shock bearing, as this is a weak point. If the owner will let you, pull one side of the dog bone and remove the bottom shock bolt. Make sure the aluminum piece holding the bearing is not all messed up. These are expensive parts, and worth checking.
Also try and rock the rear wheel to check rear wheel bearings. These are cheap to replace, but might help get a little reduction on price.
Look for any repairs to radiators, as this could be a sign that the bike was raced hard.
You will just have to trust the crank bearings, as there is little that you can do to check these.
Good luck.
Rick