If you have a tent or caravan the cheapest holidays in Aus would be ones that have free camping or low fee camping. They usually have toilet and shower facilities and some sites may have power. If you want to stay in cabins or motels, then your best bet would be to look at online websites for deals on the best prices.

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Camping is a cheap, fun family getaway. I stay with family when I go away, saves me heaps on accommodation. Then I just have to find travel costs! We split food and entertainment

Networking with family and friends at home and overseas can help with travel costs.

Combining your trip with a visit to family or friends can certainly save on costs.

That all depends on your version of ‘cheap.’ It’s good if you have family to stay with while you’re away, big savings on accommodation

Out of season travel can be much cheaper than the peak season. Finding cheap places is always time consuming during all seasons.

Last Minute deals are the best if you can handle the stress of booking last minute. Indo countries are cheap, but I am over them. Also, house sits can be ok, umm, and cruises are mega cheap, all included fun for all ages, except for grog

Well it really depends on what you mean by cheap. This could mean camping, caravanning or a 2 Star motel rather than a 5 star.
I find travelling inland is cheaper than staying on the coast. There are some beautiful places around Oz that aren’t heavily publicised.
If you below to an Automobile Club (eg RACV, RACQ, NRMA, etc) most of them have driving holiday ideas on their website + some will give you a Motel or Caravan guide for free or small $.