With the requirements you list, it sounds as if this site is going to need at least some form of ASP or PHP based coding, as well as a suitable SQL driven database. Very time consuming, especially if you're new to it - I'd hire someone else to do it. Once the site coding itself is done, many sites can be updated from within themselves by users without knowledge of the code. You're still going to need someone knowledgeable to maintain it however.
Even the basic concept of the site itself seems to require a lot of effort - do such socialising sites have to be regulated in any way; would the site be operating as a business?
Definitely a tall order, even for a team of people.
