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). You have to submit at NVC, NVC's job is to collect the documents for the consulate and make sure they are complete.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. 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: Us passport (bio page). Us green card (front and back). This guide will clarify what domicile is, how to establish it, and the documentation you need for proof of domicile. Typically, in order to claim US domicile, the Affidavit of Support sponsor must be residing in the United States.