Last time I had to rent in Australia, which was 5 years ago, it was a combination of the newspaper and property managers. I went to each real estate agent in the area I wanted to rent, and they each had a large list of every property available in the area. Some they had keys for, which they gave you in exchange for your ID, so you could go look at them on the spot.

It's a lot more common in Australia for people to use property managers, and a lot less common to have large commercial rental properties. I believe gumtree.com.au and housemates.com.au are both popular now.