Understanding Multisite Meta

I’m quite new to WP multisite and i’m still having trouble understanding fully how the user meta works in a WP multisite.

My objectives are this:

– Build a network of 300 sub-sites based on 10-15 templates (the NEW BLOG TEMPLATES plugin will be a huge help)

– Each sub-site has 1 external user (who is our client)

– Each external user has their own profile (names, specialties, zip code, etc)

– This profile can be viewed by other external users on the network. This is the part where i’m having trouble with.

What is the best way to allow other external users view another external user’s profile, search (by radius) and connect with another external user?

Any pointers are appreciated.