Ellay, as far as advertising I`m not quite sure how to help you, but just a thought you may want to consider before you chose a hosting company for your site, be sure to read their End-User License Agreement as well as the Terms of Service. Some service providers have restrictions on what content the sites they host can provide.
I`m a little confused on who exactly you are in this process? Are you the writer and you are looking to self publish or at starting an adult publishing house or something else?
As for advertizing, in my opinion it`s actually easier to find targeted groups of adult audiences. I don`t have any research on this, but it is my strong personal experince that sex positive folks are above average in their use of the net for community building, education, entertainment etc. For many folks they can only find something in commom with people who live thousonds of miles away, but no one in their home town. So my advice would be to selectively target groups. Writing a story about kinky lesbians? Target their websites, biggest blogs, stores, web zines, newsletters etc. Many large cities have community groups focused on a specific flavor of sexuality and the biggest all accept advertizing for their newsletters.
And then there are the tons of adult fan fic sites out there. They are free, but you could build up a following to drive interest in your site.
Best of luck!