What is none of the jobs end up being what you're after - or if you don't get accepted for any of the offers? You've already traveled that far and you've done

What is none of the jobs end up being what you're after - or if you don't get accepted for any of the offers? You've already traveled that far and you've done what they've asked you to. What you do in your spare time is your business. I see nothing unethical about paying for your own return flight to Sydney/Melbourne/Brisbane to extend your chances at employment.