I am thinking it would be pretty easy to build a barrel barge along the lines of this and launching it on the river:-
http://www.angelfire.com/ultra/edaskew/genbarge.html
I wouldnt have any power. Or water. Garbage would be a problem. But as long as there is no engine on the boat I wouldnt need to get it surveyed, I think.
I know you can't build a mooring on the river without getting permission from the Council, but are there any laws against anchoring on the river, even permanently?
Google liveaboard.
e.g. http://www.cruisersforum.com/forums/f74/living-aboard-in-qld…