If it is hot, and they bust the guy and he tells them who he sold it to, they can come to you and seize it and you'd have to go after the guy in small claims to get your money back. But as long as you cover your butt with proof that you paid him fairly, like Atlanta_man talks about, you wouldn't be charged with possession of stolen merch.
Is the VIN on the block? If so, run it with your local PD and if it comes back clean I wouldn't worry about it.