I sure wish I didn't miss this one the first time around.
THere are no good units sub $100 right now. Your only real hope is to look on KIJIJI or Craigslist or even Ebay for a used Logitech MOMO if you want a good wheel for that budget. All the other units out under $100 are basically garbage and won't live long or work well.
THe best advice I really have is to save up the money to get the G25/G27. Yes I know the price is way way up there, but you get what you pay for. If you want any realism at all, this is about the lowest entry level pricing that offers true realism. I've had most wheels made by Logitech and the MOMO is the only budget that I would ever recommend while the G25/G27 is THE unit I recommend.
Remember this, really good setups START at $500+. This is no a hobby for the meek.