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. 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).This tool is to assist you in determining what, if any, financial evidence you submit with your Affidavit of Support. A declaration is a simple statement that you intend in good faith to return to the United States to resume your domicile. This guide will clarify what domicile is, how to establish it, and the documentation you need for proof of domicile. View the sample form here. This guide will explain how to prove domicile when filling out Form I-864 ("Affidavit of Support"). Consular processing support without the high price tag.