We need to select a social networking platform to build off of. Social engine is a really good PHP-based platform we could start with. The have a great demo site setup at: http://demo.socialengine.com/ It's for food vans but you can see all the capabilities it has.
It has Members, Albums, Blogs, Classifieds, Chat, Polls, Forum, Events, Groups, Videos and Music .
You can see the feature list here but I think it's worth the cost: https://www.socialengine.com/buy-social-engine
This content is created by the open source Your Priorities citizen engagement platform designed by the non profit Citizens Foundation