It is hard for another person to tell you what to do, best to follow your heart la.
But for initial accommodation, I highly recommend one of those furnished rentals: http://www.stayz.com.au/
You can book well before you travel. Just pick a suburb you may like or know and choose one that suits you best. You may also ask for special rates when you are staying for longer than a month. They are great value (in fact not much more expensive than other rentals as they provide all furnitures, beddings, weekly cleaning and all utilities including internet and phone!) and give you ample time to get settled down and choose which suburb you finally like to buy or rent. Many of these furnished accommodations are run by small groups or even privately, the owners/operators are usually happy to give you a reference for subsequent rental applications, this reference IS VERY important.
HK300萬 equivalent to AU410,000 (today's rate)
well....maybe enuff to buy a house (depends which suburb do you have interest)
You will stay at Sydney, right ?