All in all, there are free slots that pay real money, but you will have to be playing at real money online casinos as opposed to social casinos on slot apps, or playing titles in demo mode.
LuckyLand Slots is a social casino, where you can play casino-style games online totally free. You can play either for Gold Coins or Sweeps Coins, and also redeem Sweeps Coins winnings for real cash prizes.