Do you think the Dollars could really exist? Just looking for opinions. A true community/gang working together doing idk....stuff?

I don't think you're in the right board for that kind of question (newbie talking..) but I'm gonna answer it anyway : I think yes, and that's probably NGOs (non-governmental organizations)..
There are certainly gang and organizations, not necessarily named Dollars, that have the same goals has Durarara's Dollars gang..
If you ththought it, it exists!
じゃね!(see ya!)