Rentals aren't from fields, but from players with extra gear. I've seen them go for 20$ to 50$ for a game, usually including some or all BBs. Check with the locals for more details.
For the few games I attended, total cost was anywhere between 10$ and 75$, all in.
As for cheaper guns, no one imports them at a price that makes it worth it right now. If you are on a budget, get age verified and browse the classifieds. Absolute bare minimum initial investment is 400$, but aim for at least 600$ to 800$ to have a decent setup.
Also, some users make irregular gun orders from overseas at a nice discount. Again, check the classifieds.
Invest in some good eye protection.