Like 50 Shades of Grey? Watch Sleeping Beauty (2011)

If you did, I suggest watching Sleeping Beauty.

The main character is a university student who needs cash. (I know, what students don't).  She replies to an ad and starts working as a series of erotic freelance jobs.

Parallels to Shades include:

> innocent heroine struggling for identity
>themes of dominance
>fetishism (but not BDSM)
>non-happily ever ending
>slightly frustrating main character 

The film is available on Netflix (instant view) and since it was acknowledged by film critics, probably available from libraries.