You are fixing your mind on the wrong thing, the goal here isn't about getting money from each other but facilitating the journey of self improvement. Even if they don't end up fulfilling their side of the bargain there's no harm done because that challenge would make the individuals work on themselves. Asides from this I don't think it's a good idea to get involved with people in anything pertaining to gambling, because Humans act different when there's money involved in something. I also prefer to bet in casinos or bet centers instead of doing it with people but I love the idea of betting for self improvement.