Before making a reservation for a cheap rental car, it is best that you check that you are eligible to do so by checking the car rental company's terms and conditions.
Most agencies will have a non-negotiable minimum age requirement of 25. Younger drivers (usually 18 to 24) will be subject to a younger driver surcharge. Even if you do meet the age requirement, some agencies will even have an upper age requirement for certain specialty vehicles. Make sure to check with the agency policies online to get clear details about the younger driver policy and your particular situation. Also note that an international company might have different requirements for each location.
Some car rental companies have agreements with businesses to allow car rentals to younger drivers who will use the car for business purposes only. Sometimes the younger driver surcharge is even waived. If you are going on a business trip, and are a younger driver, it would be best to consult your company's corporate travel manager for further details.
Most rental companies need a guarantee for the rental of their cars. Therefore, they will require your credit card information as a deposit. (Most, but not necessarily all, major companies do not accept cash deposits).
Having a history of driving offenses will understandably influence your eligibility to rent a car. The better your driving history, the better chance of renting a vehicle. The best thing to do is check the company's policy regarding driving records prior to pickup.