Bandwidth Sharing Software???

[FlasHBurN]

I am going to be moving in with a friend soon and we were planning on having a network and dsl for our computers setup. Because of our downloading habits and what not we dont wanna steal each others bandwidth, so we were wondering if there was some sort of software setup to say limit the amount of bandwidth each computer uses? Maybe even a feature that will allow a user to go over that amount if it isnt in use by the other?

Anyone here know of anything like that? Or even if theres a feature like this built into a specific router?

Thanks!
eric