How to start casino heist GTA 5 online begins with players needing to acquire a high-end apartment with a planning board. After purchasing the apartment, players can initiate the heist by completing a set of prep missions, which involve gathering equipment and choosing a crew. Players also need to unlock the casino by accessing the location and scouting it out for potential entry points. Once prepared, teams can begin the heist itself, aiming to successfully steal the loot while evading security and law enforcement. Coordination and strategy are key to achieving victory in this adrenaline-pumping mission.