Looking for an idea for a niche business directory

I'm looking for ideas for a business directory where businesses can find business partners and interact with other companies. There would be 3 types of memberships: free, business and premium, which would offer different levels of interaction and business 'visibility'. At the same time I do not want to overcomplicate it for users with multiple layers of memberships to pick from.
I understand that social platforms offer the ability of creating different communities and enable communication within them. However, I'd like to keep this directory as an independent website.
I do not attempt to compete with Google Places, but believe there is still a place for niche directories, where one can find businesses with specific profile or a commercial need.
Thank you.