Providing proof of domicile in the United States is critical for most people when submitting Form I864, Affidavit of Support. 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.You must live in the United States or a U.S. territory and have proof of domicile. Must meet the financial requirements. 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). The sponsor must provide evidence of status as a U.S. citizen, U.S. national or lawful permanent resident. Joint sponsors don't need to prove domicile. The petitioner needs to prove domicile or the intent therof.