MOVING FROM TORONTO TO MELBOURNE

hi,

I am 19 years of age, and am a Realtor in Toronto, Ontario, Canada. My mother(48 years old) is working for an airport company and has been doing so for the past 15 years, and my father(50 years old) is driving and part shareholder in a taxi company, in Toronto. Also we have a investment in developmental land, and own a very decent house. I am a Toronto native and my father and mother have been citizens for over 20 years. We love our nation and admire everything its given us. With this said, my mother's two sisters and their respected husbands are located in Melbourne. Also my father's brother (who is married to my mothers sister, i know its weird!) is situated in Melbourne. My father's brother is also in the taxi business in Australia. We have no family here in Toronto, and as my parents approach and elderly age they want to be close to their siblings, so it is only a natural thought we move. I was wondering what the procedure would be for us to be able to permanently move to Australia would be and become Australian Citizens?
Also would this mean we would have to give up our Canadian Citizenship?
How long of a process would this be, and how much would it approximately cost?
Also if we are to move there, which business' are currently thriving there? My father of course would join in with his brother in the taxi business, but I would need to start something as well.
What is a respectable down payment on a decent business?
I am into real estate already, and I have completed my first year in a bachelor of arts program in University here, however i am not really concerned with education at the moment, but do look to pursue it in about 2 years, and more concerned with being settled first. Hence the Realtor career path and it is quite a passion of mine.
So please if you could help me I would really appreciate it. I have no knowledge of this situation at all, I had never even considered leaving my beautiful city, however sometimes you have to move due to certain circumstances.