Finding a social network (I think) plugin

So I want to construct a website that basically allows users to identify their favorite food trucks, hot dog vendors, and other mobile food sources; not only by name but also by category (truck, cart, etc). AND The mobile food vendors should be able to know who their fans are (who has marked them as a favorite). The vendors should be able to post updates – new location, hours, etc.

This means users (fans) and vendors need to be able to login and have an online usernames. Initially everything will be free but eventually I hope to monetize it by offering an upgraded (paid) account to vendors which would allow them to post specials and coupons as well as send mass emails to all their fans.

Now, I think this would be a social network plugin but I am not sure and, even if it is… there are nearly 700 social network plugins. How do I find one that will do what I want?

Does anyone know of such a plugin?