Earlier quoted context omitted.
Many people do all kinds of jobs they wouldn't otherwise do for survival. Sex isn't magically different from backbreaking manual labor.
Back breaking manual labor is not legal, or rather you can be forced to pay rather steep fines for doing it. (The definition of the words we use is key here)
What I meant in the first place (which I think was clear to begin with, regardless of language) is that many people make choices to do jobs they wouldn't otherwise because they need the money. Many jobs are taken for survival. Prostitution isn't really significantly different than any other undesirable job, aside from the emotional significance that we often assign to sex. But there isn't fundamentally anything about sex that differentiates it.