for my two pennies worth, its clearly a different situation in different parts of the world, but sex trafficking, to my mind, is where a person is bought/kidnapped/smuggled from one location to another and made to engage in sex with other people. Its against the person's will, ignores their freedoms including freedom of choice, and has to be wrong under any situation.
prostitution/rent that is a free choice of the individual concerned, where they do not feel obligated or forced in any way to engage in such actions, is not sex trafficking?
There have been tv shows here in the uk, talking with both men and women in the sex industry including young men/women using it as a means to support themselves through university, older woman acting as dominatrix (where there is no penetrative sex involved) to gay men who just see it as a way of getting more sex, that show its not a straightforward equation.
For every forced person, there is another for whom it is a deliberate choice. so this is about control, control of the situation, and who they see, what they do etc.
If prostitution were legalised then it would offer some protection to the group who actively choose to make a living this way, but it would do nothing to get rid of the black market trade that goes on.
as to whether its right that someone sells their body for sex, that is a moral judgment for individuals and that judgment should be respected whichever side of the argument people fall?