I don't know much about Windows license stuff, but I just wanted to warn you that Windows Server 2008 R2 is 64bit ONLY. If you were planning on updating his existing server, you would want to validate that it has a 64bit capable processor.

As for remote access, there are some interesting things you can do if you have Windows Server. Some of the ones that I'm a little familiar with include Terminal Server gateway (connect to remote network servers using Remote Desktop without requiring a VPN connection), RemoteApp (run a Windows application on a remote machine, but have it appear as if it is running locally), and DirectAccess (VPN without the VPN). I mention these with the caveat that I've used the first two, but have no idea what is required to setup/maintain them.