A site to find professional GMs: https://startplaying.games/
It seems some/most of the GMs charge a fee: $10, $15 or $20 per hour seem like common rates. Not sure if this is per player or for the whole table. I would guess the whole table. I mean, they aren't doctors or lawyers lol.
Others charge by the session it seems. And it seems the rates are indeed per player.
Never would have imagined back in the '90s that people would be able to make a living out of GMing. But now it makes sense once you realize where everything is headed: live "movie" direction sounds a lot more respectable than "dungeon mastering".