Generally, a young woman decides to be a prostitute as a job. I have lots of story written in my head about how she goes about it, all the steps she goes through to set-up her body and her manners and her intelligence to be more appealling -> setting up a front business -> keep lists of clients in case something happens to her, etc. But there are a number of things left unanswered to write and actual story.
-Who is this girl? What was her upbringing? Was it highly dysfunctional? If so, does she even realize that it was dysfunctional? How does that come out in the story? Is she a reliable narrator? How do I make her a sympathetic character while not making it a story where ALL the reader does is pity her?
-Why does she do this instead of some other regular job? Or even something legal, like stripping? Glamour? Money? Power? Manipulation? How does she cope with trading her body for money? What starts her on this journey, what event in her life? What does she plan on doing when she can't do this anymore?
-How to frame the story? I want a first-person narrative of her telling her story, but why is she telling this story? To whom is she telling it? or does it even need a framing device?
--Most important--What is the plot of the story? I'm building, or at least trying to build, a great character, but where does this story go? After she becomes who she wants to be, what does she do with that? How does she feel? Does this come back to bite her in the ass or does she live a happy life?