Hi!
I'm a sociable person, we can discuss the all part of this project.
I observed that this project it's a big platform, for this I suggest to use a strong and complex framework like Laravel (the latest versions Laravel 5.1, Laravel 5.2), I have some experience with this framework.
We use PHP, HTML, CSS, some jQuery, maybe JavaScript, and I suggest to use MySQL Database, MySQL is all we need for this project. MySQL Database is very good for this project (of course if you want we can use the MongoDB database) but MySQL it's very good for this platform, look at Facebook platform (the big social platform) one of the database that Facebook use is MySQL.
MySQL is a tabular database, is good for us, we create more tables (for users, for user role and so one..)
This project is a huge platform, It's hard to work on this, only one person. I'm more good on the back-end part, I create the login page, register, encrypt password, system of roles for users, the profile details, posts, comments... and so one.
I suggest, for a good development to buy a template and I can start to code it, to write function and so one, or you can employ a new person for make the front-end part, design.
I can do all things, front-end and back-end, but takes time.
I chose a longer period of time to complete the project because, maybe during development appear bugs, error, so I have time to fix it.
A longer period means "Think twice, code once", for the best result of this project we need time.
Regards, Alin