Hi darko, how are you.
I have a suggestion here. Maybe you can add a link for each of the agent properties.
It seems similar like adsmanager
http://www.joomprod.com/index.php?option=com_adsmanager&page=show_ad&adid=104&Itemid=36 <-- 'See all ads from username', when you click on the username it will appear the posting of all relevant object from the agent.
I think this will help the buyer to find the good and the best agent.
2nd is, are you planning to create a posting limit for a different types of user? like Registered user = 2 posting only / Special user = 100 posting.
However your works is really great. I'm still testing it on my localhost before launch it to real site. Thank you