Domain file access sharing or transferring amongst users

I help out with a site my friend hosts, however when he set it up, he put it under his main user account. Now I’m at a point where I need FTP access and this isn’t possible without being given access to the 20 or other sites he has under that account.

Since you cant have multiple users on a single account, how would one transfer the site to a new user so he didn’t have to worry about people having access to things they shouldn’t without having to remove and rebuild the site?

You can set it up to host under a new user in the panel. It’s usually a very painless process. Every site should be run under its own user anyway.