I'm sure that this has been suggested before, but Pawnshops,garage sales,CraigsList, and the like are good places to find a quality used biccyle. Look for a reliable name brand, and if it is cheap enough, you can take the bike to a good bike shop and have it looked over, tuned up, and maybe put new tires on it. In the long run, this would be more economical then going the Walmart route.