Think the deal you're getting on your rental car is too good to be true? Well, it probably is. Rental cars are often a necessity when planning road trips and travels in different states and countries, and it's hard to pick apart all of the different little things that add up to total cost of renting. However, the number you're quoted isn't always the number you're charged at the end of your trip, and it's usually because you missed the fine print and got charged a hidden fee. Here's what to look out for when renting a car.