Is it illegal for a homeless person to sleep on the street? Can a person get arrested for this?

in a lot of cities/towns today the answer is yes. Usually there are tent cities outside the city limits. None of the sleeping places (from what I understand) are safe. Your better bet would be to move back with family or with friends who own a home so you can stay a little longer. It takes from 3 to 9 months to get back on your feet so when staying do help out with maintenance or errands or running for errands or washing the car, cutting the grass or something so you can help pay your way.

if it was illegal the prisons would be overcrowded

it would be stupid to be illegal cause the government won't help them

In some cities, yes.

The cops can come along and hassle you anytime they want. As a homeless person you have no real "rights" - at least when nobody's watching. If the newspaper is standing there with cameras, THEN maybe you have lots of rights.

Depends on local laws.

yes but only if the city prevents it.