Kgoul,
As an example, just so you can get some figures as a base .... using an average fuel cost $30 per hundred kilometres, as I dont know if you are wanting to go into outback areas, or just stick around the coastlines, will give you around 8300 kilometres of vehicle travel in a Patrol with a $2500 fuel budget.
Another thing to consider, is that the back floor of a Patrol is not flat, and you would also need to factor in a bit of work to make it comfortable