Production would pay the clue bearers, instructors, and performers a fixed amount for a certain time commitment. This is essentially an entertainment industry standard. In the event some racers lag behind (e.g. Mark at the Bollywood dance Roadblock in TAR20), it may convert to an overtime bonus for unforeseen circumstances. As for venues, they would book them in advance following the regional jurisdiction or establishment owner's prices and requirements. It would be similar to planning for a fair in public places and banquets/weddings for private events.
I could be wrong, but maybe Peach, Neobie, or someone more familiar with how Elise and Bertram handle this could clarify/verify.