20 C.F.R. § 416.1104
We have described generally what income is and is not for SSI purposes (§ 416.1103 ). There are different types of income, earned and unearned, and we have rules for counting each. The earned income rules are described in §§ 416.1110 through 416.1112 and the unearned income rules are described in §§ 416.1120 through 416.1124 . One type of unearned income is in-kind support and maintenance (shelter), which we value depending on your living arrangement. These rules are described in §§ 416.1130 through 416.1148 of this part. In some situations we must consider the income of certain people with whom you live as available to you and part of your income. These rules are described in §§ 416.1160 through 416.1169 . We use all of these rules to determine the amount of your countable income-the amount that is left after we subtract what is not income or is not counted.
20 C.F.R. §416.1104