To claim an unrelated relative as a dependent, they must live in your home the entire year, AND have less than $4700 of taxable income, AND you paid more than half their total support.
Remember that even though social security disability is not usually taxable, it counts as support they provide themself. You would need to add up their cost of living (including the value of the home you provided, and any other support, plus their travel, medical, entertainment, and so on); and then determine if you provided more than half of their overall financial needs.
