Coming from a country with minimum wage laws I don't understand how you survive when doing an unpaid internship. Do you just have to live at home and sponge off

Coming from a country with minimum wage laws I don't understand how you survive when doing an unpaid internship. Do you just have to live at home and sponge off your parents while you are interning? Or do you just have to get deeper into debt while you are interning? How long does it take before you start getting paid?