Cash is not an option when you arrive at the counter, as the car companies do not accept cash upfront. However, if you use your debit card or credit card at the beginning of the rental, they will use that to hold the funds for your rental until you return the vehicle. Some companies do accept cash at this time when you are returning the vehicle and they know the exact amount owing. If you want to use cash to close out the rental at this time, you can ask the car company if they will accept cash to close out the rental, then you can drop off the car, go inside to the counter and pay cash, releasing all money held on your credit card.