Please don't buy your bicycle from Wal-Mart. I'll gladly buy my little cousins one from there, but not for anyone who is older and not for anyone who is really looking to ride often or commute. I'd say an new entry level bike that will grow with your needs and last a while will run roughly $300-450. However, if you're not looking to spend that kind of money (1 car payment?), Craigslist is your next best bet. And if you're patient enough or not in a rush, Craigslist is better than buying new, IMO. Find your frame size, find the style of bike you want, set your max price, and search for bicycles $50-100 higher than that price and be ready to bargain. Good luck!