The person's gross TAXABLE income for the year must be less than $4,050 in 2017.
Social security doesn't count as income, for the income test, nor does workman's compensation or non-taxable disability income*. But that money he spends on himself does count as support not provided by you, for the support test.
*Not all disability income is tax free. If he receives a W-2 (with an amount in box 1) or 1099-R, the income is considered taxable.
