Relevant questionaire text is as follows:
If a person is not related to Person 1, mark the applicable box. A “Roomer or boarder” is someone who occupies room(s) and makes cash or non-cash payment(s). A “Housemate or roommate” is someone sharing the house/apartment (but who is not romantically involved) with Person 1. An “Unmarried partner,” also known as a domestic partner, is a person who shares a close personal relationship with Person 1. A “Foster child” is someone under the age of 21 who is involved in the formal foster care system. For all other people who are not related to person 1, mark the “Other nonrelative” box.
At first I assumed a roomer or boarder would be someone who makes payment to the head of household who is an owner, but this does not seem to be the case. Roomer/boarders are present in renter households.