The likelihood for a sensible return on your investment in GA flying is very low, I'd estimate around 5-10% likelihood of actually getting a return that pays off your investment and allows you to support your family. This is based on the number of jobs out there, and the range of payscales. I'm talking UK/EU here but I would imagine it's not that dissimilar a picture in Australia.
You need to really really really want to fly for a living, plus work bloody hard for a long time, and have a decent amount of luck to get to a sensibly paid position in GA.