Any U.S. citizen or legal permanent resident can the the Sponsor of a family based immigration petition if they satisfy the income requirements. The Sponsor has to sign an affidavit of support for the Beneficiary, in which the Sponsor guarantees to maintain the standard of living of the prospective immigrant at a level not lower than 125% of the national poverty level until the Beneficiary has become a U.S. citizen or has been employed in the United States for 40 qualifying quarters.