I did nude modeling for an art class a few years ago in college. It's pretty easy, and I got paid pretty well.
You do poses anywhere from 1m-1hr, and the longer ones are more difficult. I didn't realize how difficult it was to stay perfectly still for 20+ minutes, and even though you get a minute break on the very long ones, you still get sore. No matter how comfortable a position you pick, you'll be uncomfortable at the end. You underestimate how much the tiny movements you make matter until you can't move at all.
Overall though, I think it was a really rewarding experience. I was obviously really nervous the first time I did it, but it was nice to overcome that challenge. I was recommended to do it by my GF who was a student in one of the classes, and also modeled at one point. Also, any time you bring it up (with any open minded crowd), people tend to be impressed and have tons of questions.
I was worried about getting a boner, but it never happened to me. The nerves are too much at first, and it's not a sexual atmosphere so I didn't have to suppress it or anything, even when I modeled with naked girls.
Speaking of which, I modeled with a couple other people (I was alone about half the time, but modeled with others). The professor liked multiple people because you could have more complex scenes. luckily, it was pretty much always 1-2 girls I modeled with, and of all my time ever doing it, I only modeled with another guy once, and at the time there was ALSO another girl there, and me and the other guy had very little contact with each other so n-no homo. I'm not sure if it's always mostly girls, but my professor said that she liked when guys were willing to model because it's much less common.
The students are always really cool, and 90% of the time between poses they are happy to let you see their work and take picsI had never been drawn or rendered by a talented artist before, so it was neat to see.
I also fucked a girl from class, shit was SO cash.