I would ask the owner what kind of maintenance that's been done and ask to see any paperwork that goes along with it. I would test drive it, test all the functions and see how it opperates and perfoms. Other things to ask are things like:
1. Has it been stored indoors?
2. Any known issues or problems that it's previously had?
3. Are you the original owner?
Take a good look at the machine and inspect it's overall condition; belts, blades, tires etc. It should give a decent indicaction of how well it's been taken care of. It should look fairly new being that it has low hours.