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. This form is required to show that an intending immigrant has adequate means of financial support and is not likely to become a public charge.Use this form to show they have adequate means of financial support and are not likely to rely on the US government for financial support. 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). Providing proof of domicile in the United States is critical for most people when submitting Form I864, Affidavit of Support. Examples of proof that a sponsor's trip abroad is temporary and that he or she has maintained a domicile in the United States may include: