Though fully appreciate that they are not a full-on competition chassis, have to suggest these as a relatively inexpensive option for a beginner:
http://www.horizonhobby.co.uk/autoon...ost_buggy.html
Have had first hand experience of one of these and have to point out that they are incredibly well made for the money, RTR right out of the box (though would suggest a faster charger) and are REMARKABLY strong and resilient!
Well worth a look as are several in the same range!