That easy eh! There's a private sale tractor I'm interested in and there's a dealer pretty close by. I was thinking of borrowing their mechanic for a couple hours to come with me to look at it. Is this worthwhile? Probably depends alot on the mechanic I guess...
Maybe look at it first yourself. If it is something you are interested in, then get the mechanic. No sense possibly wasting his time and your money if your paying him and it is a turkey to start with.
Look it over for the obvious, abuse, leaks, drive it to see if everything works. If you like what you see, then get a pro if you are uncomfortable making a decision.