sharing dsl with client using usb modem

The isp’s of course don’t want you to be able to share a dsl line for small
“home” type networks so they usually provide a USB type DSL modem.
The inexpensive DSL routers tell me you gotta have an Ethernet style DSL modem and you can’t share the account using them unless it is ethernet style – for
IP gateway on its nic – Well I think it can be done without setting up a proxy
server – software like winroute etc should allow this – but I have never done it. Can anybody advise ?
Want to share a pc running 98se with its working USB single DSL account.
PC is currently networked to a NT 4 PDC
and there are two other clients – another 98se client and an I-mac all
on 100 T with internal TCP/IP.