How to setup a wireless network for as little $ as possible?

I have already a computer with DSL internet. Now I would buy a second PC, place it in the room right next to where the first one is. I have a couple questions. First I want to know what is a decent wireless router that is as cheap as possible. All I want from it is that it is stable, and that it can easily output the signal through a single wall and maybe 5 meters of open space. I don't need powerful security features, firewall, extreme speed or whatever. Just want it to work and not be too slow.

Second thing, what does the computer need to be able to receive the signal? Are there motherboards with an integrated receiver, or does everyone has to buy an adapter PCI card or USB device? Again I want to spend as little money as possible.

I live in Canada so if you want to check prices use www.pricecanada.com

Thanks.