Many jobs are somewhat like that, but it's a matter of degree. Compare the market price of the job to the price that would lead people to want to take the job.

A lot of people would be willing to become a janitor at 3 times the market wages for janitors. A lot of people who are physically able to do construction work would take the job at 3 times the market rate for construction work. Not a lot of people would be willing to become a prostitute at 3 times the market rate for prostitutes.

This means that prostitution is much farther on the scale of "forced into by circumstances" than janitors or construction workers.