maybe go over and tell him you are convinced you want to try dirtbiking and you can buy in at 19 unless he has lots of gear that will fit you and some spares like sprockets etc after you admire his rig. i bet you can leave with it for 20-21 if you keep it friendly. one of the things we all hate as a seller is a guy that starts picking things apart or starts off with something like 'i hear the powervalves on these were"breakers" and hard to service, and the crankshafts don't hold up, and second gear goes out often" etc. looks like a decent price even at 23, but again i would probably go for the ktm first. the kx is way prettier.