Hi, i came across a site that says you can use wordpress to create a site like kijiji or craigslist. It's called classipress from appthemes or another one I forgot the template name. There are some components you can use from Joomla as well to make your Joomla site like a classifieds ads site. I would google it or check out the info here - http://www.enzolina.com/web/creating-a-classified-site

-jane