The Concordia Student Union's Off-Campus Housing and Job Bank (HoJo) is a great place to start searching for off-campus housing. You must be an undergraduate student to have full access to the website.
HoJo also offers a variety of resources to help you with off-campus apartment hunting:
Legal information, handouts and referral (not advice)
Workshops on your rights as a tenant and worker
A place to conduct your job/housing search (free phone, internet, newspaper classifieds, maps)