Everyone who immigrates to the United States under a Family Visa Petition must have a financial sponsor. A financial sponsor must be a U.S. Citizen or Lawful Permanent Resident and he/she must complete an Affidavit of Support. The Affidavit of Support is a contract through which the sponsor agrees to provide basic support to the immigrant so that he/she will not need to rely on public benefits such as Food Stamps and Medicaid.
If you sponsor someone who becomes a Lawful Permanent Resident and that person is later given public benefits, the agency that provided the benefits to the sponsored foreign national may require you to reimburse the agency for the expense incurred. Additionally, if as a sponsor you do not provide basic support for an immigrant you have sponsored, the immigrant and the agency that provided benefits can pursue legal action against you.
The affidavit of support remains legally enforceable and your obligations under the contract will continue until one of the following occurs: (1) the sponsored immigrant becomes a U.S. citizen; (2) the sponsored immigrant can be credited with 40 quarters of work (usually about 10 years); (3) the sponsored immigrant loses or renounces his/her lawful permanent residency and departs the U.S.; or (4) the sponsored immigrant dies.