In order to claim someone as a dependent, one test is the support test.

You must provide more than 50% of support. With that said, if you provide $4000 of support for the year and your child buys a car for $4500, you cannot claim an exemption because he provided more than half of his own support.

(So if you’re a parent, offer to pay for enough to cover half, you’ll get it back in taxes and come out looking like a good parent)