The minimum age to get hired and work at Mcdonald's is 14 years old but you may have to be at least 16 to do some jobs at Mcdonald's.
Either way while working at Mcdonald's it's a good idea to search for other higher paying jobs since Mcdonald's doesn't pay all that well but it's a good first time job to get some money and job experience.
I worked at Mcdonald's for 2 years and then I found another better office job that paid much more and is where I work now.