Why would you just connect two computers together? I assume he'd want access to the internet and therefore, you need a router. You could get a hub but, hubs operate at layer 1 of the OSI model and, therefore, have collisions, stealing your bandwidth. I am a firm believer in the use of switches.
Also, if you're just going to connect two computers directly together, you need what's known as a "crossover cable". The transmit and receiving pins are changed to that the two computers can "talk" directly to each other. If you want to set up a network connecting the computers to a switch, switch to a router, or use a hub, you need what's known as a "Strait-thru" cable. Besides, most routers come default "plug-and-play" with a DHCP server. Of course, I'm the guy who likes to mess with old, cisco 2500 series routers just for the fun of it