I am trying to build a server for my wife's home based business. I will buy a server machine & server software?

look up using terminal services. it runs the program remotely on the server from the other pc over the internet. what type of business ? its that a server generaly is used for a lan [ intranet system ] inter office communication. other then that you would need a high bandwidth internet connection to make use of a servers full capability for serving web or e commerce. you can use remote access for accesing outlook over the net from another computer with out server software or a server.

You can do it, but the results won't be spectacular. If you're not expecting much from it, it should be fine. You'll probably want to get a video card in it of some kind, though; servers aren't easy to configure when you can't see what you're doing! :)