Check Craigslist or ebay. Perhaps some club members have something that will fit your budget. Check bikesdirect.com there may something there that will work for you. They have some bikes on sale that fit your budget.
Have you tried Craigs List they usually have a good selection under bikes just a lot of looking. You need to know what size that you will want to have and what options and how much they cost so you don't get taken for a RIDE so to speak.
bikesdirect.com has a sizing chart for the bikes they sell. Note Bill H. and Junkman are correct that you need the right size bike. If you get a poor fit, then you will end up hating the bike.