Very few enter voluntarily, and over 70% of prostitutes were sexually abused as children.
2 in 5 of all sexually abused children go on to have some experience in the sex industry - be it stripping or porn acting or phone sex or prostitution. The average number of clients is 11, with some prostitutes just doing it once or twice, and others working for life with clients in the thousands.
Some of us were having an argument the other day or two with libertarians (one of whom got zotted) who claimed that prostitution should be legalized. Scum like that refuse to see the facts, such as your comment.