If you want to sponsor someone for a family-based green card, you need to provide proof of a U.S. domicile in your Affidavit of Support (Form I-864). These additional financial sponsors also have to submit an Affidavit of Support, proof of their income, and proof of their legal status in the United States.Completing and signing Form I-864 makes you the sponsor. File the Petition for an Alien Relative (form 1130), and. File the Application to Register Permanent Residence or Adjust Status (form I-485 ). The petitioning sponsor must sign and complete Form I-864, even if a joint sponsor also submits an I-864 to meet the income requirement. Most users should use Affidavit of Domicile (MPC 485). If you need to save a partially filled-out form, you may choose to use the alternative form:. Providing proof of domicile in the United States is critical for most people when submitting Form I864, Affidavit of Support.