If travelling north up east coast check out the backpackers car market in Kings Cross Sydney. Plenty of cheap vans and cars (usually with camping equipment etc) for sale there. Everything on sale needs to be vetted by garage beforehand and seller will have list of faults etc so get fair idea of what getting. If going for an older vehicle recommend going something like a 4 litre like a ford falcon or holden commodore as they've probably taken the punishment they're usually dealt by backpackers better than say a 1.8 japanese import. Love to be back there, Enjoy!