You'll be laughing with $5k a month spare if you're a couple with no kids, even if you eat out a few nights a week and go out boozing on the weekends. You'll only start burning cash if you're going up and down to Sydney etc on a regular basis, flights and hotels will soon add up.
Public transport is very cheap compared to the UK and getting about is easy, once you're in the CBD trams are free and cost next to nothing if you use them outside of the free zone, and it's just a few bucks to travel a few stops out on a train
