Based on the details you've given, you may be able to claim your son as a dependent, but -- because he was over the age of 18 and not a full-time student -- he is not a Qualifying Child for purposes of the EITC.
Since he is not a Qualifying Child, then he must pass the tests to be a Qualifying Relative in order for you to claim him as a dependent. Since he is your child and (assuming) you provided more than 50% of his support, then it comes down to the amount of money he earned in 2016. If he earned less than $4050, then you can claim him; if he earned $4050 or more, then you cannot.
Here's a link to IRS Publication 17 which covers all the requirements for claiming dependents: https://www.irs.gov/pub/irs-pdf/p17.pdf
