The contract signee, the main driver, must be at least 21 years old in the majority of countries and some as France accepts drivers aged 18 years. Drivers must hold a valid driver's license for at least 1 year.
For drivers between 18 and 25 years of age, depending on the chosen car category, additional insurance is required and must be paid for on site when the vehicle is picked up.
You will need to pay additional insurance for each additional driver on the contract. The rate depends on the driver's age, contract duration, the chosen car category and the rental location.
Important: in some countries, there is an age limit for the elderly as well.