According to the Houston Chronicle, there is no minimum age requirement to join a limited partnership or start a sole proprietorship. However, most states require corporation owners and members of limited liability companies to be of legal age.
Rules on limited partnerships vary from state to state, but there is no legal minimum requirement for minors who wish to join in limited partnerships. They may register businesses and make executive decisions, but many states require a parental signature when filing a limited partnership with the state. Likewise, some states have laws that affect the enforceability of contracts signed by minors. In cases in which a business is registered by a group of minors, a parent of legal age may be designated to sign contracts on the group's behalf.