This is a term related to male on male contact. It describes a fetish (sexual attraction to objects, body parts, or situations not conventionally viewed as being sexual in nature). Where one party is clearly homosexual or bisexual. And the other party is "mostly" heterosexual. The heterosexual party is normally given money to have oral sex performed on him. This act is not about the money or prostitution but, sexual excitement towards the opposite sex that would not normally be there.
College male student that has never been with or thought about doing anything with another man it offered 150.00 to let this guy give him oral sex, it would be totally discreet the guy accepts the offer and enjoys it. Later he trys it with another guy for free and does not enjoy it. He is paied again and enjoys it. (this example is where all the oral pleasure givers look the same and do the same quality job) so the "college guy" only enjoys same sex when he is paied it is a Gay4Pay fetish.