Hey Melboy,
Congratulations on making it through to the final interview.
It's that dreaded two week wait for you, I feel for you.
In answer to your question, once you receive the call you must then proceed with the medical, which will take a few days at best for you to get everything done.
Once you have passed your medical and received your contract, if you are not currently working, you will be able to start as soon as possible.
I had to give notice at work so had to wait one month, but another guy from the last Melbourne interviews left at the start of the month, so it all went very quickly for him but he wasn't working at the time.
I hope this helps and best of luck to you.
TanyaD