Internet Connection to house.
1 Modem/Router connected to WAN Internet connection(DHCP Networking)
1 4-port or HUB/Switch in the room with the PCs
1 Long CAT5e cable running from modem/router to the Hub/switch room containing the PCs
3 Shorter CAT5e cables from the Hub/Switch to the PCs
3 Power Strips with at least 6 AC outputs each(1 strip per User and you should have a few extra AC ports left in each) for the Hub/Switch & room Fans.
If you run into power issues which you shouldn't with three machines, stick one rig on another circuit. You should have a few 20 Amp circuits in the house and worst case you run an extension cord from another room for the last PC. This shouldn't be an issue though.