You can do small jobs at pretty much any age, but to have a real job you have to be 16, & There are other jobs that are more advanced & you have to be a certain age. It really all depends on what you want to do.
okay. there are many different jobs and the question was vague. but a lemonade stand or mowing a lawn or babysitting could be classified as a job, so someone could be very young. in re some of the replies above saying 14 - there are no real employers who hire younger than 16 that i have ever heard of. and if i were 16 and looking for work i would include these younger/previous "jobs" on my app. or resume.