Ideally you find someone's garage queen but those are tough to come by in the ATV world. Craigslist and Facebook marketplace are likely the easiest resources to keep your eyes on for deals. Or a local consignment auction if you have any of those nearby. If I were looking for a used quad I think I'd pay particular attention to the exterior... A lot of scratches and dings are a good indicator that someone used it as a beater or potentially rolled it. A brand new 500+ cc quad is going to run you 8-11k... So I think if I were you I'd consider whether I wanted to gamble on a used one, or save a bit longer and go brand new with warranty. I got a great deal on a new one with winch and plow. It was a prior year's model and they were trying to move stagnant inventory.