Looking for backend member based cms

I have very specific needs for a backend cms. Any suggestions for a cms, commercial or open source that has these capabilities. If it has a front end thats fine but it must have a strong intuitive backend for very computer illiterate clients.

  • Good user management roles that are subscription based, the user only has access to their profile, but can upgrage to more feature rich profiles.
  • Intuitive preferably ajax based user interface or dashboard
  • Custom text fields with image upload support
  • Database
  • Scalable with good security standards

It is kinda of like a classified ad based cms, where a user logs in, adds all the relevant info ( credit card, custom form fields) and uploads some photos.

EXCEPT I do not need any front end, yes its weird. I do not need anything web based on the front end besides a login.