Create a Classifieds Ads website, using WordPress

Create a Classifieds Ads website, using WordPress. If possible, we would like to have an intelligent upselling/cross-selling system in operation on the site. Although this could be added, after the initial site is developed. There will need to be the following user accounts: The main, Admin account - This will be for my use, maintaining the website. One Editor account - This will be the main "admin" account, used by my client. Author accounts - One for each of multiple other websites' classifieds ads sales staff. Each of these other websites serves a specific area. Contributor accounts - These would be for site users, who are buying and posting classified ads, on the main website. One exception to the normal WordPress user role permissions, is that these contributors should be able to publish their own classified ads, once they have purchased and submitted them on the website. They need to be able to purchase, submit, edit and delete their classified ads, from the front end of the website. The other (area specific) websites (which may or may not be running WordPress) will need to be able to have a page on their site, which pulls in the listings for their area. For example, a website in Biddeford, Maine would only want to show a page, containing the listings for the area in and around that city. Since these other website may be running on many different platforms, I believe the best way for those sites to do this would be to pull the appropriate page, from the main classifieds ads website, into a page on their site, via an iFrame. If you think there would be a better way, please let me know. The site needs to automatically push a post out to various social channels (Definitely Facebook and Twitter. Possibly others, such as Instagram or Pinterest), anytime a new classified ad is added to the site. All ads should be posted to the main social media accounts (belonging to the site's Editor account). Ads for specific areas should also be posted to that area Author's social media accounts. The website needs to have ad management capabilities. Both, self-service (for Contributors) and placed by Editor or Author accounts. I am considering this plugin: WP PRO Advertising System - All In One Ad Manager [login to view URL] I am considering the following themes, for this website: Directory Engine - [login to view URL] Directory Builder Pro - [login to view URL] ListingBuilder - [login to view URL]