Mac desktops forum: minimum MAC set-up for simultaneous users

Actually you can.. there are ways to use X11 to output to multiple displays, standard in Linux. Also, if its a Mac server and you're using workstations, then depending on whether they're thin clients using server based software or having a single desktop with a thin client connected to (i.e. a Windows server with an RDP connection, i believe up to 3 are supported including the console connection).
Considering that Apple RDP uses VNC it is possible to make a remote user see an alternate desktop, and certain applications are able to run multiple instances if they are intended to be used as such. When I was in middle school we had LCII workstations with like a 40MB internal hard drive with System 7 and an SE30 as the server with MS Works and most of the software on it. Some computers had external HD's..What he wants to do can be accomplished with a Mac Mini server and two thin clients with embedded OS's that just connect to a remote desktop, or one thin client and one person on the console. However I would strongly recommend a processor that supports multithreading and has multiple cores. In many cases it is possible.. especially with Virtual Machines, to divide up your resources accordingly.. The same can be said for virtual/remote apps, etc..
Distributed computing has come along way and the people who are smart enough to realize the cost benefits can reap huge savings by maximizing their hardware resources so that you don't go out and buy full desktops with bundled software when you could get a server and thin clients that cost half as much, serve up embedded OS's, and deployment of apps and such is a breeze. Theres no need to worry about imaging computers or any of that crap and it makes licensing WAY cheaper and simpler. For a home user 2 users is fine if the software permits it. But honestly you're gonna need two computers or at least one thin client that will run apps on the remote server and just show you the display over the network.
Its amazing how simple this model is yet so many old dogs are reluctant to do it and end up wasting time and money doing things the old way.. Thats why i'm done with IT after a decade...I will put my experience and BA in MIS to use in other ways where I'm not somebody's biatch that has to implement policies made by ignorant superiors.. unless of course I find something where I call the shots..