Sleeping in a car or someone else's house doesn't have any rent. You don't have to pay for things like electricity, gas or water if you don't have a place of your own.
A friend helping out in an emergency for a few days, weeks or mayyybe months is one thing. Systematically living on somebody else's bill only to save your own expenses is something else.
You're of course free to do what you want, but don't be surprised if your friends get tired of you.