I also bought my Baja-5b used from another member here and haven't been sorry. A word advice on the clones, though, is to THOROUGHLY go through them and tighten, LocTite and fluids where necessary.
A word of advice: Don't do it! There is almost no OEM part support and little to no aftermarket part support. Save for a bit longer and get a name-brand such as Losi, Traxxas, HPI, Associated, Tamiya, etc.
If you can find one from a reputable seller (like this forum or our sister forum Largescaleforums.com), you shouldn't have a problem. I bought my HPI Baja-5b from another forum member and have not been sorry. (Thanks again, @Nitrobuzzard).