Welcome to the forum:
Look for the usual stuff. Tire wear, condition of chain and sprockets, engine oil,etc. Check for scratches, dents, broken parts,lights, see if any warning lights are on. The Basic stuff you would normally check. I don't know of any particular problem that is inherent to the Versys, other than the fact that it is highly addictive. lol But most important. Check the color. Green is the best (in my opinion) and White is a jewel (the color I have). However the other colors perform just as good. Well maybe the green is a little faster. It looks like it is. If It's not, it should be.
Hope you get the bike and enjoy it as much as we all do. Many of the people on the forum can help you with mods you may be interested in. In my opinion, the first mod should be to raise the front of the seat a little. Cheap mod, but helps a lot. post pics of the bike when you get it.