Hi,
Here is a link for you to have a look at
Classifieds and try the demo of it.
It offers categories and subcategories of unlimited depth, variable fields per categories, image upload for categories and classifieds, locking categories, classifieds approval, classifieds management by user, auto-generation of thumbnails and customizable e-mail notifications.
And it's open source, so you can hire someone to tweak it to suit your needs.
Hope this helps.
