You cannot work until you have commenced your course in Australia. Once your course has commenced you are permitted to work a maximum of 40 hours per fortnight when your course is in session, and unlimited hours when your course is not in session.
Work that is a formal registered part of your course is not included in the limit of 40 hours per fortnight.
Voluntary, unpaid work, is not included in the limit of 40 hours per fortnight if it:
is of benefit to the community
is for a non-profit organisation
is genuinely voluntary (that is, you are not paid either in cash or other—board and lodging is acceptable).
If the voluntary work could have been undertaken by an Australian resident who would have received a wage, then this is included in the 40 hours.
If you are a postgraduate research student:
you can work a maximum of 40 hours per fortnight during any preliminary courses you undertake
if you have commenced your masters by research or doctoral degree in Australia, there is no limit on the number of hours you may work.