Hey bud, if moneys a big factor then you may wanna rethink "RACING". It cost. now as far as getting a RTR for $400 - thats gonna be hard. Im looking out for you in the long term. Do you wanna pay $400 for something that you cant find parts for at your LHS. How about $400 for a POS that will break just jumpin off the curb.
I would suggest, and I hate to say this, but the Asscocated RC8 RTR..
Team Associated RC8RS Race Spec RTR Buggy $489
Team Losi 8IGHT 2.0 1/8 4WD RTR Buggy (w/DX3S Radio, Telemetry Installed & Starter Box) $650 - - - BEST DEAL ON THE PLANET
These are easy to find parts for and support is very good. thats just me and my opinion