To qualify, the child must be under 19, under 24 if a student or any age if disabled and must live with you for at least half of the year and receive at least half of their support from you. Dependent relatives who are not your children need to have gross incomes less than $3,800 and need to depend on you for half or more of their support.
The link that Christian shared is to work at Starbucks's in Greece. In the U.S. you have to be 16. The hiring age can vary according to the youth labor laws in the state that you work in. Source: I work there and was hired at age 17.
In order to work at McDonalds depending on the company/owners you have to at least be a minimum of 16 years old. You have to be sixteen in most states, however, You should check the legal age in your state. In order to work at McDonald's you will have to be 16 and have a permit or driver's licence. You must be 16.