The costs to get the car on the road are called "on-road" costs. These vary with new and second-hand cars.
All cars need to be registered in your name at your nearest Roads and Traffic Authority. At that time you must also pay Stamp Duty, to transfer ownership of the car to you. You also pay Third Party insurance (CTP - called a Green Slip in NSW), to insure people other than you who might get injured if you cause an accident.
For second-hand cars, at registration, you might have to get a roadworthy certificate (a Pink Slip) if your car is more than 3 years old, depending on where you live.
You can choose to get a vehicle inspection before purchasing, which will give you an indication of whether the car has been looked after or has been in a major accident. It's usually a good idea to get a REVS check. This online service checks the Register of Encumbered Vehicles, to make sure that there are no outstanding debts on the car.
For new cars, there is a dealer delivery charge, to get the car ready for you.