Yes, that's a big problem almost everywhere in the US and certainly most everywhere that is on the "more afforable" variety. You absolutely need a car. I guess the only bright side to that is that 20 year old beater cars are pretty cheap.
I know nothing about Hattiesburg. It sounds OK for the deep south. They even have a synagogue and a gay community center. But I checked apartments and it looks like you're talking 900 for anything not horribly depressing. I can afford like 350, ha ha.