To make life easy for you it would be a good idea to get your previous Real Estate agent (if you have rented before) to write you a reference on letter head saying that you paid your rent on time and kept the property in good condition._ If possible get a couple of references from different Real Estate Agents if you have rented a few properties.

It is also important to prove that you can afford to rent the property, if you have a job in Australia a reference from your employer stating that you work for them and in a full time position etc is fine._ If not a bank statement showing that you have sufficient funds in your account.
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This should be sufficient, a landlord wants to know that you will look after the property and you will pay the rent on time.

In regards to references/documentation, you will need tenancy references, personal references, copy of passport and visa and conformation of employment. If you have not secured employment yet, we will require a copy of a bank statement confirming that you can support yourself during your stay.

A personal reference should be from a person who knows you in both business and personal life. A reference should state how long they have known you, what sort of a person you are, in what capacity they know you, and their opinion of you financial stability_(without going into depth)
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Comments such as " .......... is of reputable character" " Is financial stable in my opinion" "alway meets his commitments" are all statements that would normally appear in a personal/character reference.