Your chances are EXTREMELY limited......
At your age Qantas wont touch you. Virgin Blue might but u gotta get a few thousand hours up on multi's. (I'm not sure but they might require Aussie citizenship, not just the right to live and work there - i might be wrong)
To build time in Oz you have to go bush (ie out in the sticks somewhere) where you will be treated like crap from most but not all operators and payed jack! Unless you are extremely lucky you will have to do one or two seasons on a single, like a C210 then they will put you on a light twin.
Thats why all us Skips try our luck here.
If a career as a flying instructor is appealing, then give that a go.