Official Staff Interpretation 202.7(d)(5)(2)
2. Reliance on income of another person — individual credit. An applicant who requests individual credit relying on the income of another person (including a spouse in a noncommunity property state) may be required to provide the signature of the other person to make the income available to pay the debt. In community property states, the signature of a spouse may be required if the applicant relies on the spouse's separate income. If the applicant relies on the spouse's future earnings that as a matter of state law cannot be characterized as community property until earned, the creditor may require the spouse's signature, but need not do so — even if it is the creditor's practice to require the signature when an applicant relies on the future earnings of a person other than a spouse. (See §202.6(c) on consideration of state property laws.)
The opinions expressed are mine and they are not to be taken as legal advice.