That makes sense. I don't know anything about the divorce laws of late-1970's Australia, was it still the case that you had to had proof of marital infidelity to get a divorce?Not a gay hooker. A hitman.
The first verse sounds more like he's interested in bumping off the teacher instead of sleeping with the schoolgirl. And the "back door man" thing is probably more of the guy starting an affair with the woman who is driving her husband around the bend, so the man can go free without having to actually instigate the end of the relationship himself. I never once thought the singer was offering to be the catcher to the man's pitcher behind his nagging wife's back, even if he was expecting to be paid for the privilege.
So remember: he wants to sleep with the woman whose husband/boyfriend/whatever is fucking her best friend, and he'll sleep with the other woman (for a fee) so that her cucked husband has incentive to leave the abusive relationship he's in.