You can do crazy and dodgy things with your character in BitLife. When you get famous enough, you can sometimes get a magazine offer to pose nude for them. While it might seem like a bad idea at the time, the money is pretty decent and some people who want to make it happen don't see it too often. Unfortunately, making the request is a bit luck-based, so you need to be reasonably patient.
You can receive the offer when you manage to become famous in BitLife. It takes a little time to become famous, usually through social media. There are five different platforms you can join, and you join when your character turns 14 when they enter high school.
After that, your main goal should be to accept offers to do advertisements and product promotions for big companies. It's a bit boring and repetitive, but the more you agree to do, the more others know how ready you are to support these types of avenues. Eventually, you'll get a notification about a magazine asking if you'd like to pose nude for their magazine. Although it's random, accepting more product promotions and advertisements increases your overall chance of your character seeing the offer.