You brought up a number of thoughts. Sex work is a continuum, and I consider myself a sex worker as an author of erotica (I'm using what is most intimate to me--mind, experience--to provide sexual pleasure to a stranger). Martha Nussbaum in Sex and Social Justice reframed the whole realm of sex work for me. Sex for service is a kink but too often a tragic requirement. I think it works well as a trade between equals but not when one is dependent and MUST barter. Like you suggest, sex for service is a form of prostitution and it's the freedom to choose our work that we want; hence, legalizing sex work. On the other hand, relationships are all about trade. People change, dependencies change, what is bartered can change. Thanks for the reflections.