You've got 3 days, why don't you go and have a look at it?
Probably has original rear shock on which could be getting ropey, and I'd be inclined to listen for possible cam chain rattle, other than that just look at general condition and maybe put on centre stand and see if wheels are spinning okay and brakes not binding.
Whenever you buy 2nd hand you tend to have to go through the bike anyway so you know things have been done for sure.
Ideally you would want to ride it but that's between you and them if that happens. (and insurers if you want to do things right)