You just have to stick to legal, regulated online casino sites such as BetMGM, Caesars Palace Online Casino, FanDuel, Betway, bet365 and BetRivers. They offer great casino game ranges and they will pay out quickly and without any issues if you win.
Casinos often offer free play as a promotional tool to attract players and provide them with a chance to try out their games. However, these free play credits usually come with terms and conditions that need to be met before any winnings can be withdrawn as real money.