Originally Posted by Mike at Taree

The car must come with a safety certificate that is provided to the seller by a registered garage (virtually the same as the MOT in the UK).

It doesn't cover things like engine or gearbox problems, basically lights, brakes, exhaust and steering.

Then you have to get a "green slip" for yourself, which is a compulsory third party insurance policy in case you run over little old ladies or plough into a crowded cafe killing diners and getting sued for millions. Cost to you will be around $400 per annum depending on a "points score".

You still need to get private insurance in case you run into a Mercedes, this isn't covered by green slips.

Ok then good to go, if you have a valid licence.

I'd disagree about the six grand, Australian used cars have been traditionally more expensive than the UK, but they do last longer (more favourable climate and no salt on the roads) and don't rust nowadays. With the advent of $15,000 drive away no more to pay prices on many smaller cars nowadays, that has really depressed the used car prices compared to just a few years ago and you should get a perfectly good Falcon, Commodore or Toyota for that price.

However as in everything it's pot luck. You can get a pre purchase test by a number of independant garages such as the NRMA (equivalent of AA or RAC) and some used car yards sell pre approved by NRMA cars.
Edit: second hand cars from a new car dealership tend to be expensive, but as they have been accepted by the dealers as trade ins they are usually keen to quit them, so some bargaining is often rewarding, if you are a good haggler. They keep the newer top end trade ins and send the rest on to wholesalers but often have a gem or two "in the pipeline" that they will flick onto you cheaper, so worthwhile trying the dealers if you have time and energy.