WA and NT with a private

Hey,

Sorry for opening a new thread but it seems to me to be on a different subject.
As I had written in my last thread we have a month to travel in WA.
We first thought of buying a 4WD but I am afraid that if I buy an old car I will not be able to sell it in Darwin even for a very low price - the people's car I had been looking at (around 4-6000 AUD) have been trying to sell in perth for weeks now, and I don't have that time for that when I finish my trip in Darwin.

So I am left with the option on Renting a private car (4WD are way too expensive). My questions are:

1. Going from Broome to Darwin with a private, are there still interesting places I can visit, making the trip worth while ? what are they ? and how long should I put aside for it ?

2. Another option is to take a car in perth and Travel in a circle around WA for a month and then return it in Perth. Isn't a month too long ? Is the outback (inland) of WA interesting or is it just long boring drives ? how do I create such a round trip ?

Pleae understand we are quite short of money so it is either one of these two option or if you think it won't be worth it we'll just cut our trip short and save the money.

Thank you

EJ