Right price for a 2002 Yz-125

Wow that is a great price if it looks mint and like it has little hours. If you're really worried about maybe there is something wrong... I would check out the clutch (remove clutch cover and pressure plate and take a look), oil, top end/cylinder/rod play, reeds, suspension, chain/sprockets, tires, spokes, radiators/fluid, brakes, air filter/airbox, subframe, frame, etc. along with a good test ride (shifting and using most all the gears and riding until the bike is hot). Good luck!