1) Rent: $425 / week = $18xx / month, Northeast Melbourne, 20km from city, 3km to nearest train station, 3 bed room house. It costs around $350 - $400 even for 2 bed unit unless you choose somewhere far away from the city
2) Electricity + Gas (winter) + Water $400 / month
3) Transport.
Japanese 2000cc car, around $25000- $30000, if you need a car loan, the interest is quite high (6-7%), may cost around $400- $500 / month
Petrol is cheap, around $1.3 / Litre, around $150 per month if you drive everyday. Car insurance is around $600 annually.
If you rely on public transport, either you live close to the shops (then the rental will be higher) or wait for bus every 30-60 mins. Obviously if you live close to the train station, rental will be higher too.
4) Food + miscellaneous (eg shampoo, clothes, diapers etc) It depends, around $2000 / month (we cook ourselves)
5) School: My girl's school: $500 annually ( public primary school) + minor charges (buying recreation books, school activities etc)
6) internet and Phone: Home broadband is $60 / month and mobile is around $10-20 / month (pre paid SIM card depends on your usage)
Actually, the major expenses are rental and food. Say, we spend around $5000 a month.
But, if you are PR, you can apply for Family tax benefit. (We apply second week after we arrive and we receive first payment in a month). It calculates your income and number of children (<18 yrs). For example, if your family annual income is around $50000 with 2 children, then you can have around $660 fortnightly from the government, no asset assessment required.
I hope it gives you an idea how much you need. Actually, I think it is quite similar to Hong Kong except for the rental.