Well, you are not going to get that much for 500 bucks. JEEP IS NOT A GOOD BRAND. It is better to get a reputable brand like Jami or Kona but first you have to decide on what you are going to use this bike for. The main categories are trail bikes,cross country race bikes, black diamond bikes,downhill bikes,mountain cross bikes and jump bikes.                                                                                                                    If you are just going around the trail now and then there is no point in buying anything other that a trail bike. The rest are expensive and unpractical. I would recommend a Specialized ,GT,Kona,Trek or Jamis is fine. Look for something with disk brakes,aluminum frame,decent front fork with more than 3 inches of travel and a rear shock but you are going to spend more money for the nicer features. Buy from a reputable dealer and don't make any hasty decisions. If you need more information buy any mountain bike magazine buyers guide or go to a dealer.