There is no minimum age to buy a car in Illinois. In IL there is no law prohibiting a minor from holding the title to a vehicle. However, the IL Secretary of State (SOS) advises caution to those that may sell a vehicle to someone younger than 18, because only a buyer 18 and older can be legally bound to a sales contract.
So as a minor it is likely that when buying a car you will be required to have a parent or guardian sign on any legal document with you, such as the sales contract and the insurance policy that you will need to place on the vehicle you title in your name if you are under 18 years of age.
While Illinois may not have a minimum age for titling a car in their name, an insurance company will normally require an adult, parent or guardian, sign on your insurance policy with you since you are a minor and your insurance policy is a legal document.
For more information on what may be required of a minor that wants to buy and title a car in their name contact the Illinois SOS and for insurance you can start shopping around here for your young driver car insurance needs.