I am doing research on assembling a team, using the right tools, and the cost to develop a highly responsive social network that is capable of dealing with a lot of users. Similar to the Facebook concept but using the basics package for now. Profile, friends, posts, updates, media upload/download, streaming, chat and Inbox messaging are all in the package. We certainly do not expect it to be as popular as Facebook or handle the same number of users and requests, but in its own game it has to be a monster, and expandable for later on.

Neglecting the hosting, and servers part, i am looking for technical advise and opinions, on what kind of team i need ? how many developers ? their expertise ?

What are the right tools ? languages ? frameworks ? environments ?

Any random ideas about the infrastructure ? Quick thoughts on the development process ? Please use references, if you have any to support your ideas.

Development cost mere estimation ? NEGLECTING THE COST OF SERVERS

I know my question is too broad but my knowledge is very limited and i need detailed help, for any help you can offer i thank you in advance.