Renting a car at Fiumicino Airport is one of the solutions available to travellers landing at Fiumicino. Being able to get to Rome on your own, and move around without having to rely on public transportation or taxis is a big advantage, but remember that traffic in Rome can be a nightmare, especially during rush hour.
Car rental companies will also obtain a credit card authorization as a security deposity against loss or damage: Your credit card will not be charged in advance, but your spending limit will be affected until you return the car.
Getting to Rome, or to Fiumicino Airport by bus is much easier and safer. You can purchase a ticket for just 8 euros and a professional driver will take care of the traffic, while you travel comfortably for a fair price.