Or rent: you can get a place to live for only $60/month. There's no running water, but it's clean and dry and it has a lock on the door. The cheapest place you can find in the US is a lot nicer, but also much more expensive.
Buses have no route maps, no shelters and no doors. They might not come to a complete stop when they pick you up. But you can ride for 25¢.
The US has a kind of minimum standard of living, but it comes with a minimum cost of living. If you can't afford that, you end up with nothing.