Sex.com doesn't seem to be that lucrative of a domain name(not 13mm lucrative)...if it was, more companies would try to rank for the term sex.

right now it's

  1. Wikipedia Article
  2. FBI Sex Offender Registry
  3. Psychology article
  4. Porn Tube Site
  5. HIV charity
  6. Virginia State Police Sex Offender Registry
  7. Music Review Blog
  8. Sex Pistols music site
  9. Georgia Sex Offender Registry
  10. Center for Sex Offender Registry

I'd bet there is a ton of traffic because people just want to see what kind of site is hosted on sex.com, so its a lookie loo situation, where you'll have a crappy conversion rate. So a traditional porn site won't work that well.

A better option would be to open a casual encounters type site(basically adult friend finder), and charge $5-10-20 bucks a month under the guise of making sure that there are no fake profiles.