The Illinois Banking Act states that banks may accept deposits from minors and that “the rules and regulations of such bank with respect to each such deposit and account shall be as binding upon such minor as if such minor were of full age and legal capacity.” 205 ILCS 5/45.1. 

The Illinois Business Corporation Act and Limited Liability Company Act both bar persons under the age of eighteen from incorporating corporations or organizing LLCs, but we are not aware of any restrictions on owning such businesses or on doing business as a sole proprietorship. 805 ILCS 5/2.05805 ILCS 180/5-1.