the money paid to him for an internship is taxable to him. if his gross income is more than $4,300 he can't be claimed as a dependent. but there may be good news. if so in 2020 he can file his own return and get the maximum stimulus of $1200 + whatever the second stimulus is if it ever gets passed. don't know if you are married or not. but if not, and you don't have a qualifying related individual (QRI) as a dependent you can't use head of household filing status
a QRI is any of the following and you paid more than 1/2 the cost of a home lived in for more than 6 months by any of the following
1) qualifying child
2) parent
3) a qualifying relative other than one who is unrelated and only treated as a QR because they lived with you for the entire year or only treated as a QR only because of a multiple support agreement
