When I had to relocate recently (2000km drive), I considered buying an old bus. All the furniture from my unit would of fitted in and I could of parked the car in the back too (via a ramp).
However the huge bonus of using the bus is that it could also be used as a home. This includes when you get to the destination! Imagine the money you'd save on rent and all that stuff.
The other advantage of the bus is that you could pick up a load of tourists at each town you pass, charging a fee. This would pay the fuel bill and probably leave a bit of profit on the side too. When you get to Darwin you could drive around the city picking up passengers all day if you wanted to.
Good luck with the trip, let me know if you want any more advice.
Tiger.