stehsegler said..
3 to 4 weeks? Not worth buying unless you are prepared to take a big hit on price when it comes to selling in which case you may as well rent.
Try Wicketcampers.com.au. It's a bit like a rent a wreck company. They buy up older vans and kit them out. You can get a van for about $60 a day. That usually includes camping gear as well.
Make sure you buy a rental car insurance from Europe before you leave. There are a few places around online that have insurance for as little as $5 per day. That's a lot cheaper than buying insurance through the rental car company. Do a google search.
RE driving in WA, especially on the way up North... things to expect: chipped wind shield, all kinds of wild life running across the the road, flat tires etc.
If in doubt don't drive at night and take it slow. Remember to fuel up. Distances between road houses on the way up North are long.
So 4 weeks = $1600 plus for rental.
Buy $3K van, sell in hurry for $2500. Cheaper....
IKW seems to have the chix sorted maybe you could include one in the deal