For real estate, I have used
http://www.mls.ca/ before but they changed the look recently and I don't find it as easy to use as before. For rent, you can check out a big rental agency called boardwalk. They are not in every city but they do have apartments in Vancouver.
http://www.bwalk.com/ I know some people who rented from them in Edmonton and the advantage is that they do everything by the book. If you rent from a private person, you can get lucky but you could also get unlucky. I had a landlady in Edmonton who was horrible, they did nothing about noise complaints, turned down the heat on the building in winter to save money (because the heat was supposed to be included) and when I left, they tried to blame me for all kinds of damages that were already in the apartment when I moved in so they could keep my damage deposit.