Is this possible?^^

Hey!
I am soon going to release a wordpress multi-site. But I want to force my users to interact with eachother.
So I thought and thought, most sites add stuff like 'like' posts and stuff like that. But I wanted to try something different. My site is going to allow users to make money,
however if they interact with eachother they make even more by learning from eachother.
That's why I want to build a forum that is displayed on the Wordpress Dashboard.
So every user that logins to their Dashboard(so every sub-domain) will see the same forum and will be able to interact with eachother.

Do you know any way to accomplish this? I saw the Communities plugin but it I am not sure if that is what I am looking for.

Any suggestions^^?

Thanks!
Mick.