If OP is needing to pay a cash payment for an apartment, that's more than just a little bit of currency to put in the wallet. Assuming we're talking about several thousand RMB, I would take AUD in crisp, clean, new $100 notes and go to a bank in town and exchange the wad for RMB 100's. Doesn't have to be Bank of China, just use a major bank branch that is displaying foreign exchange rates in the window (showing it deals with Forex at that branch). You'll need your passport for the exchange. Then pay for the apartment and use the leftover for petty cash, until you need a refill at which point you can use your ATM card.
To get from airport to town, you will need some upfront RMB so just exchange a small amount at an airport bank counter. The rates for AUD spread a bit wider between airport and town than for USD, so you will do a bit better if you wait to exchange most in town.
The one thing I wouldn't bother with is exchanging in Australia, as you'll almost certainly get a poorer rate.