Let me just stop you right there and just STOP AND FORGET about this idea IMMEDIATELY. Just do a simple google on off the plan property purchase in Australia and you'll find hundreds of reasons why you shouldn't do it. But in a nutshell, this is what you need to know.

1) Foreigners buying in Australia are only allowed to buy new properties, i.e. off-the-plan properties.
2) Developers are selling off the plan properties at a future price, i.e. the price at the estimated completion date, not the current price. Which means you are doomed to lose money when you buy an off the plan properties. Just google and see cases of people not being able to even secure loans after the building is completed. I.e. you bought the unit for $600k and at completion, the bank value it at only $550k, and you'll need to scramble for the $50k gap.
3) If the development does get completed (That is a big if as A LOT of big developer goes busted half way and you have no way to claim your money back), you see a lot of cases where the finishing is different from the actual spec, i.e. the floor space is smaller, ceiling height is lower, floor plan get changed etc.
4) Because of point 1, the off the plan market is different from the REAL Australian market. In one sentence, it is the inflated Chinese market, and a lot of them just need a channel to siphon the money out of China so price is secondary concern.
5) Due to point 2 and 3, you'll see a lot of people selling at completion, and it is sold urgently at a lesser price.

There are obviously exceptions and it is still possible to find good purchases. But if you are not familiar with the market, it is a pure speculation with very very high risk. So again, STOP NOW!!