CA|ble modems and networks

How do I go about sharing a fixed IP cable modem (provided via the digital cable company’s box) to the LAN at home. They have muttered about using two network cards in the main box then use the sharing techniques in Win98 to make it shareable (not sure if this allows multiple access)
Any and all help welcome. I do know someone who has managed this with a router but this is expensive option
Thanks
D