My mom just bought a new house, and we want to install a wireless router which is not bought yet, but we want to offer the internet to the people that rent upstairs, but we don't want to get raped by overcharges if they decide they leave a torrent window open 24/7.

So before buying a wireless router, is there one that will permit me to somehow manage the bandwith used by different users? Obviously it shouldn't be limited for us.

It could be some other way than with mac adresses, could be with some kind of user account or something. What do I need to look for?

Thank you!