I don't know what average prices in the Atlanta market are, but around me $100 only MIGHT get you something nice, that is both guaranteed to be a) 25+ years old (nothing wrong with that), and require a complete overhaul (nothing wrong with that, so long as you budget $60-100 on new parts and are willing to learn how to do it yourself, or pay $150-200 for a shop to do it all), or are willing to take the chance what you are buying is just stolen. That said, jump up to a $200 budget, and you can generally find quite a bit in rideable shape, hybrids bought with the best of intentions that made it around the block twice and are now just taking up the space in the garage that the SUV with the kid seats could be parking in.

For that cheap of a budget, I'd be watching the thrift shops around you.