What is the best way to allow users to link themselves to specific nodes?

Ok, here is what I am trying to accomplish. I have 2 roles set up on my site we will call them buyers and seller. I also have set up content types called companies. I need a way for seller to associate themselvs several companies (currently set up as individual nodes). Ideally these sellers will search the site for companies and tag the node with their uid. On their profile page I'd like seller to be able to see what companies they have tagged (companies they represent) to enable edit/delete.

The second role, buyers, need to be able to search the site for seller based on their profile fields AND what companies the sellers represent. I assume that once I figure out the first part I can use views to accomplish the second. From this point I want buyer to be able to add users to their buddy list.

So far I have set enabled usernode and profile on my site. I have looked at several modules such as favorite nodes, free tags, node relativity, relationship node linking, etc to accomplish this first task of linking users to conent. It's unclear to me what module will provide all the flexibility needed. Can someone provide a solid recommendation????