Scenario

You are not in Australia / NZ. Probably you are located internationally and applied through a job portal or job seminar in your country.

Good Answer

1. Give a fixed salary. If you are really trying to migrate and prepared to work for less, then you may want to probably give a lower salary rate.
2. I believe its not a good idea to answer by saying that you will accept any salary. This sounds very unprofessional. The company / recruiter might think that you simply want to use them as a 'stop-gap' to initially come to Australia and then will hop on to another job after joining them.
3. Infact you should positively try to show a commitment to the recruiter, and stick to your first job for atleast 2-3 years (assuming that you made it).