In the far west of Queensland, for example, the roads can be unsealed and around the Gulf it is common for a road to only have a single width of tarmac. This is not a humorous suggestion. Road trains need all the road and expect on-coming traffic to head for the hills. They have trouble deviating and will wipe out a car rather than endanger their entire load. There are a large number of car rental agencies, both local and international.
Competition means a range of prices and short-term specials, the options are worth investigating.
Recognise that while unlimited kilometre rates are common around the cities, country and remote driving can incur a higher flat rate plus a kilometre charge and don t forget insurance expenses. Smaller companies are often cheaper and it is worth shopping around. They can be accessed on the Internet. A valid driving licence is essential and applicants usually must be over 21. One-way rentals between major cities are available but not very economical.