Can a minor (someone under 18) buy a car without parental consent?
The general rule is that a minor cannot enter into a contract. If the minor does enter into a contract, then the minor can, at his or her discretion, cancel the contract. Upon reaching age 18, the minor can affirm the contract, in which case it is enforceable. I have never actually seen anyone sell a car to a minor however, without parental consent. Of course, if the minor is emancipated, the rules change.
Then there is the problem of getting insurance. The insurance companies will not give insurance to a minor without a parent on the contract because they know the minor can cancel the contract.