Landlords in most states are free to inquire as to their applicants' and tenants' immigration status and to reject applicants who are in the United States illegally. As long as landlords don't use immigration status as a mask for illegal discrimination on the basis of race, ethnicity, or national origin, such a practice is not illegal. Notable exceptions include the federally subsidized "Section 8" program, which requires proof of legal residence before tenants may participate; and New York City, which has prohibited landlords from inquiring as to their tenants' citizenship or immigration status for years (NYC Admin. Code § 8-107(5)(a)).

As of January 1, 2008, however, all California landlords are prohibited from inquiring as to their prospects' and tenants' immigration and citizenship status. (Calif. Civil Code § 1940.3.) The law also forbids any municipality from passing laws that direct landlords to make such inquiries. Landlords may still require documentation that will determine or verify the financial qualifications of an applicant, or to verify the identity of a prospective tenant.