I BELIEVE THAT SEX WORK is when you have a job that stimulates sexual thoughts in a person mentally or physically. Some sex work is mental like dancing at strip club, posing for Playboy, or writing dirty stories. Other sex work is physical, like being a porn star or a prostitute. I worked in a dungeon as a dominatrix way before I had even had sex (when I say “before I had sex,” I mean “before I lost my virginity”).
If your intent is to stir up sexual thoughts, you are a sex worker. On the other hand, I do not believe if you are a nude model at an art school that you are a sex worker, because the job of nude modeling in that context is to be a human subject, not a sexual object.
Depends on who you ask, doesn't it?