The most important problem to you now is not about money. It is which Visa do you want to use. Skill migration Visa 189/190 very depends on the occupation about you or your spouse and make sure you can pass the point test(At least 60 points). If you you have a friend in OZ that are willing to hire you, you may use the Visa 457. There should be some more Visa type that let you become PR/TR which I do not familiar with. You can consider the problem about money after you make sure you are able to migrate to OZ. For me, I will feel very comfortable if I can bring HK$10M to OZ. HK$5M for a house/apartment, HK$5M for the living cost for coming 10 years. You can start you career by this 10 years time without worrying about money, which 10 years should be long enough.
Just like in Hong Kong, when you have already paid off your mortgage, the living cost is not so much a problem and may be under your own control according to your need and desire (well a balance between them )