Spectrum hobbies makes several good points, you need to be sure of what you are buying. This goes for engines or any other thing you are buying. There is nothing wrong with purchasing a used engine as long as you do your homework and know who you are dealing with. I have a feeling several of the listing mentioned were from E-bay. I buy and sell on e-bay all the time. One thing I check out is the users feedback rating. If they have alot of negative feedback, I would avoid them at all costs. There are some good deals to be found but if you are not careful you can get ripped off. I recently purchased a demo 3w-240 from Bobby at Cactus Aviation, engine looked new and he included a 3yr warranty, even threw in a prop. I saved about 500 bucks by going this route. Point is he is a reputable business man who stands behind what he sells. I would not hesitate to purchase a used engine from him.