If he was under age 24 at year end and lived with you more than half the year (except for temporary absence while away at school), you can most likely claim him as a dependent.
He is not required to file a tax return if the $5510 was his only income and it was reported on a W-2. If federal income tax was withheld, he should file a return to get a refund.
If his income was reported on a 1099-MISC or no form, he must file a return to pay about 15% of self employment tax.
If he files a return, he needs to indicate on his return that he can be claimed by someone else.
