I know some top bodybuilders, and I am sure none of them have ever done gay for pay stuff. Other dodgy stuff yes (eg protection and money collection, nightclub doormen, dealing etc, but G4P never. I do believe it happens, but lets not get mix up and think every pro does it. You probably do get the occasional homo or pervert, but I think it pretty rare.
Ok, I’ll take the bait: what makes you so sure? Are your top bodybuilder friends independently wealthy? Have they always been wealthy? Or do they “not seem like the type”?

I simply do not understand the “if I don’t know about it, it doesn’t exist” mentality of some people—and this mentality is certainly not limited to the darker side of bodybuilding.
Most bodybuilders who do this sort of thing prefer to be discreet about it so it is only logical that you wouldn’t know what they do to raise money.
A true story:
When I was on the gay muscle/escort board about 10 years ago, I can recall one up and coming bodybuilder who joined the board and made it clear he was looking for a sponsor. He was very specific: unlike many of the less dedicated muscle wannabes on that site, he wanted ONE substantial sponsor he could “work with” rather than a handful of a small johns with small wallets. In other words, he wanted a full time body building sponsor and was not willing to hustle for nickels and dimes. He was already in excellent shape and made it clear he was willing to do whatever it took to get ahead.
Soon after he appeared on that site, he disappeared and never came back. Eventually, someone started a thread about him asking whatever happened to him. The moderator reported that he found the sponsor he was looking for and consequently had no reason to remain on the site. He concentrated on his training and the sponsor who made it possible.
Today, he is a competing pro and I chuckle every time I see him on stage or in publicity photos, magazines, etc. If I told you his name you would recognize him immediately.