From Avis you can hire a car from about R7 027 per week on average.
Generally, for a better deal it’s recommended to book in a timely manner (to save up to 3%). Cheapflights recommends you book around 16 days prior to your deserved date. Booking as early as you can also increases the likelihood that you’ll get the ideal car.
Yes, hiring a vehicle in Patagonia for a month is certainly possible.