The goal of the gay men is to determine which of the residents is the straight guy. If they are successful, they split a cash prize of $5 million dollars between themselves.
If, however, they are not able to do it and the straight guy ends up being one of the last two players standing, then HE wins a cash prize of $1 million dollars all to himself while the gay guys get nothing.
The kicker is .... none of the twelve men are gay. So for two months, we get to watch a bunch of straight guys trying to prove to each other that they are more gay than the other ones.

-"BB"-