When you say 45 to the city, do you mean by public transport or driving?
You could go to the bus, train and ferry website (131500 dot com dot au), and see different travel options to the city and other places and how long they take.

We currently live in Revesby, which is about 30 mins from the city by train and 45 mins driving. I think the suburbs around here would have houses in your price range. My friend bought a house in the Seven Hills area last year, which she says is a nice and affordable area.