I really wouldn't buy used if I was you. The main reason being that as a user of such a serious RC car with advanced engineering (these things are not just set up and go like monster trucks), you need to have a complete understanding of it yourself, and this is learned mainly from either building the kit, or even if you get an RTR, to set it up for first use, breaking in the engine, setting the brakes, tweaking the servos and clutch, etc. These lessons are important if not only to give you an extra appreciation of the vehicle.

Also, of course, you can never know what kind of condition a second hand car is in, especially if you have little or no experience of the type of car you are looking at.

With regard to your choice of car, it all depends what you are planning on doing once you get past the bashing stage, and learn how to drive the thing reasonably well. If you may want to get into racing...seriously, take a look at the Hyper 7 PBS RTR kit, it has a lot of stuff for the money, and it's a competitive, legal racer straight out of the box, unlike the mayhem RTR, plus it's about $100 cheaper I just discovered.

That's my two cents...