You may contravene the Consumer Act in your State if you do not have a cancellation policy or terms and conditions that are understood by the client, and therefore agreed to, at the time of booking. If you do not provide this information to them, then you have no legal right to withhold any deposit you have charged or claim for damage the client may cause during their stay.
Deposits: You are running a small business which is unlikely to have the ability to fill a late vacancy caused by a guest cancelling close to the date of the booking. You may have turned away other business because of the booking. You should have a cancellation policy to cover this eventuality so that you are not entirely out of pocket. You cancellation policy should state the amount of deposit, or percentage of tariff, you charge; whether you will refund all or part of the deposit and the time scale for doing that. HAA has a template that is available to members which can be customized to suit your intentions.
Terms and Conditions: Your terms and conditions cannot be discriminatory, for instance it is against the Equal Opportunity Act to stipulate that you do not accept children. However, you can include a condition that any breakages or extraordinary cleaning required as a result of actions by the client during their stay will be charged for. You will certainly require terms and conditions if your business accepts pets. Whatever you include in your terms and conditions, it is essential that your clients are aware of them and agree to abide by them at the time of booking. It is not enough only to have the information on your website, it should be included in your booking documentation.
If you are not sure as to what to put into your cancellation policy or terms and conditions a simple test as to the rights of the consumer is to run the information past your Consumer Affairs, or Fair Trading Office to see what they would advise a disgruntled consumer.
For other information is available see the website of the Australian Competition and Consumer Commission (ACCC)