Hi James,
If you are buying a car from a private seller than a
limited part of the Australian Consumer Law applies.
The three Australian Consumer Law guarantees that apply to you a private car sale transaction are:
- Clear title,
- Undisturbed possession, and
- Undisclosed securities
The guarantees protect you if for example, the person you are buying the car from isn't the owner with the right to sell or the bank knocks on your door trying to reclaim the car because there was still money owing on it. You can have a look at this blog post for more information:
Faulty Second Hand Car? Your Options as a Buyer - Legal Blog - LawAnswers.com.au
Contract law governs the transaction between you and the private seller when the ACL doesn't apply. For example, if you were mislead about the car in some way by the seller directly or by the advertisement then you may be able to ask for your deposit back or to ask the seller for the cost of any repairs needed.
Why have you changed your mind about the car?