From the August 2012 issue of Entrepreneur
Many states allow a person age 18 or over to freely enter into contracts and other business arrangements.  That means a teenager under the age of 18 may not.  Therefore, if you are 18 or over and live in a state that considers the "age of majority" for contracts to be 18, you can move foward full steam ahead (unless, of course, your business involves the purchase and sale of alcohol or other items with an age restriction)!  Just be sure to double-check with an attorney in your state that 18 is, in fact, the cut-off age for you.