I feel like you don't even have to trick people to get them to sign that deal. In fact this could be a real profession with people lining up to take a paid position like that.
Just go late night to a bar, get everybody drunk, then find the one who's wasted, let them sign an "autograph" on your "business card", order them a margarita, let em lick some salt from your tummy, done! 😘
Even though it looks low budget, it's an inventive enough premise and it looks like it has some promise. The supposed "jump scares" actually look like the weakest part of the film.
