You will need an ADSL Router which will connect to the internet via BB modem and share it among the networked computers. The firewalls will need to be installed on each of the networked computers. Each computer will also need a wireless network card (NIC).
WiFi Router - Netgear MR814 / WGR614 OR Belkin 802.11g Wireless DSL/Cable Gateway Router F5D7230uk4 OR Belkin ADSL Modem With Built-In 11g Wireless Router F5D7630uk4A
WiFi NIC - Netgear WG311 OR Belkin 802.11g Wireless Desktop Network Card F5D7000uk
It will be cheaper to buy from Savastore.com or Ebuyer.com