Non-server versions of Windows are not multi-user, meaning that only one user can be logged in at a time, total. This means one user at the console or one user logged in via RDP.
In order to have multiple users connected, you will need to invest in an edition of Windows Server that provides Remote Desktop Service, which means purchasing Windows Server and then additionally purchasing Client Access Licenses for the number of simultaneous users you need to support.
Note that Windows 7 Home Premium does not provide an RDP server at all, only Windows 7 Professional and Ultimate have an RDP server available (and of course it is single-user).
UPDATE (added by question author)
Windows 7 have 20 concurrent connections limitation, it means network connections (e.g to single SMB share). But when it comes RDP - read above.