I think one and only one DSL line is all that you need to build your home network. Front end the DSL modem with a wireless (or wired) router from LinkSys and then connect all your PCs to that router. Some setup is required for your PCs (with respect to IP Addresses) and also for the router. But manuals should help you with that.
There is also a web site which has forums that discuss home networking. Here is the link: