On my site I list alot of working backpackers which find you fruit picking work, and one of the requirements before they will find you work is that you must have a valid tax file number, and permission to work in Australia.
If you want a cash in hand job you will have to approach farmers and ask them directly. 95% of the farmers these days are employing workers which have a tax file number. The days of cash in hand work is getting harder to find.
