If you have a local commercial lawn mower shop I would stop by ,and ask if you can talk to their best mechanic. I would introduce yourself to that mechanic,and see if he or she would be interested in making some extra money on their time off work? Offer to pay for this mechanic to go with you to the location where this used mower is at, you are interested in buying. This mechanic can inspect it for you,and give you his or her opinion about the mower. Of course you or the mechanic will prob want to take a mower jack,and some basic tools for the inspection.