If you claim him as a dependent, he must file his own return if he has W-2 wages over $6300 (2016). If his W-2 wages are below that number, although not required he would have file a return in order to receive a refund of excess withheld taxes.
As xmasbaby0 said, the filing threshold if his earnings are reported on a 1099-MISC (instead of a W-2) is $400.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
