You can't rent 4x4's in that range per month. But I think you can lease them or have yearly contract with the car rentals for around 3500 minimum. On the other hand I'd advise you to get a 4x4 on installment, even if its a 2006 model and if its in a good condition, it will cost you a lot lesser than a new one. Something like a Nissan Pathfinder or Toyota Prado.