I am pretty sure it is the same everywhere.

Ex..
You play a slot for $1. You use the $1 of your free play. If you get a winning line for $1 you are paid in real money. Your next spin is $1, this also comes from your free play. You do not start using your cash until your free play is gone. The smart thing to do with free play is play your game of choice and calculate how many spins you will get with the free play. If you play the $1 machine you should spin 35 times and then cash out. If you want to keep playing that machine that is fine but I would still cash out and start over fresh. This is just my take on smart free playing.