Congratulations on getting PR.
in answer to some your questions, there is not a minimum timeframe that you have to be PR for a loan.
Being a casual worker will not necessarily stop you from obtaining a home loan but the longer you have been employed with them the stronger your application will be, as well as being potentially open to more lenders.
If you do go permanent full time, we have access to lenders where you will only need 1 payslip for a full pay period.
You can find out your potential borrowing power here:
You will also find a stamp duty calculator here as well which you may find useful.
Generally you will require a deposit of 5-10% of the purchase price and normally a Lenders Mortgage Insurance charge would apply when borrowing over 80% of the purchase price (the amount payable depends on the insurer and can be added to the loan in some cases). Stamp duty will also be payable on the purchase.
If you require futher assistance please don't hesitate to get in touch.