You can find information about the minimum age of the renter by clicking the More Information hyperlink when you're viewing a specific vehicle.

When you select the Book Now option you will also be shown a More Information tab

When you click More Information, a 'pop-up' screen should appear. Here, you will see a lot of information related to the vehicle and the agency. On this screen you should see 'supplier terms' like below:

You can also select the Terms tab and then Drivers License & Minimum Age

The following should appear:

The required age may vary depending on the car rental that you choose. The usual minimum age is 20 and sometimes higher for larger vehicles.