Hi Joy,
The Sunshine Coast is probably not abound with free and low cost camps.
The closer to the coast the more expensive the camp generally.

If you dont have it, download wiki camps, as it is a good app to have on your device to quickly and easily locate all camps and parks in a nominated area.
The other thing to remember is parks and other camps are very busy from end April to October during the annual migration of nomadic types from the southern states.  

Happy travels