JD used to put hour meters on their mowers, so check to see if it has one. This doesn't mean it wasn't replaced or unhooked, but it could have the correct hours on it.
Check to see if the spindle bearings have any slop in them and if they are greasable. Lift up and down on the end of a blade to check this. There should me no movement. A slight movement still can be OK if you keep the spindles lubed good, but no movement at all is best.
I usually pull a dipstick on used equipment to see what the oil looks like. If it's clean and on the full mark, at least it seems to have been taken care of.
It depends on how many hours are on this machine what the value is. See if you can find out the hours and let us know.