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).If you have a joint sponsor, they must also complete Form I-864. Providing proof of domicile in the United States is critical for most people when submitting Form I864, Affidavit of Support. If you are filing Form I864 as the petitioning sponsor, use our How to Fill Out Affidavit of Support Form I864 guide. Completing and signing Form I-864 makes you the sponsor. Us passport (bio page). Us green card (front and back). Villanova University is a closely connected academic community with renowned faculty, rich resources and a personalized, supportive learning environment.