It really depends on how it was ridden and how well it was serviced/maintained. As an example, a bike with 10K miles that was well-ridden and taken care of would be much better than a bike with 3K miles that was redlined to hell and never serviced.
Like mentioned before as long as the maintenance of the bike has been kept up then it should fine. Ask for the maintenance records if he took it to the dealership and if he did the jobs himself then talk to him about it and see if he sounds like he knows what he's doing. I'm willing to bet though if he did things himself then he kind of knows what he's doing...to a certain extent. Get a feel for the bike and the owner and how it is and then come back here if you have any more concerns or questions about things (sounds, sights, etc).