@Terrificli -- that one can be hard to answer as cases are considered on their individual merits. However, contract law generally suggests that the contract cannot be enforced against the minor. Of course, that's not all there is to it.
If, for example, let's say a 17-year-old enters into an agreement to buy a car and tells the owner that he is 18-years-old. Prior to turning 18-years-old, the buyer decides he doesn't want the car. The contract is probably not enforceable, but that does not mean the 17-year-old gets a free car. He will probably have to return it.
Using that same example, let's say the 17-year-old does turn 18 and keeps making payments on the car. If he decides he doesn't want it, he can't simply void the contract and claim he wasn't old enough to enter into the agreement. Why? In that situation, the former minor ratified the contract and made it effective by continuing to make payments on it.
Still, that's not all cut and dried. If the law was simply a matter of plugging in fact patterns and getting results, every attorney on the planet could be replaced by a massive computer that could spit out correct answers.