If you're immigrating to the United States through a family member, or else through a job where your own relatives submitted the visa petition or own at least 5% of the petitioning company, then your petitioner will have to show a willingness and ability to act as your financial sponsor. The purpose is to help prove that you are not inadmissible as a potential public charge (you won't require financial assistance from a government agency within the U.S.). (See 8 USC § 1182(a)(4).)
The requirements are strict. Whichever family member signed your petition (to start your immigration process) will also need to submit a lengthy document called an Affidavit of Support on USCIS Form I-864, which lays out how much income and assets the person has. If the amount isn't enough under the U.S. Poverty Guidelines, or if the U.S. government demands more assurances, the immigrant will need to show proof of personal assets or have additional U.S. citizens or green card holders agree to serve as sponsors.
The Affidavit of Support on Form I-864 basically promises that the U.S. family petitioner will pay the immigrant's living expenses so that the immigrant does not have to rely on assistance from a government agency within the U.S. (whether state, federal, or other).
The petitioning U.S. family member must show that they earn (or have saleable assets worth) at least 125% of the income needed to support their own family as well as the immigrant, plus the immigrant's spouse and children if they're immigrating with the immigrant. That amount reduces to 100% for military families.
Exactly how much income is needed to support a certain size family is computed every year by the federal government and published in a document called the Poverty Guidelines. This can be found on USCIS Form I-864P.
If, for example, you're an immigrant marrying a U.S. citizen, and there will be two of you living in your house (no children at all), then your household size is "2." Look on the appropriate row of Form I-864-P to find out the minimum amount that your U.S. citizen will need to show in earnings to overcome the public charge ground of inadmissibility in your case. In 2022 for example, U.S. petitioners would need $22,887 to support a household of two people.
You'll need to meet the guidelines for the year in which your Affidavit of Support is filed, even if the required income levels get raised or changed later (which usually happens around April). Such subsequent raises won't affect your application.
Even among petitioners who would ordinarily have to fill out a Form I-864, various exceptions apply.
First, if the immigrating person has already worked legally in the U.S. for a total of 40 "quarters" (as defined by the Social Security Administration; it's about ten years), no Form I-864 affidavit needs to be submitted. In fact, in an interesting twist, immigrants can be credited with work done by their U.S. citizen spouse while they were married.
So if you are an immigrant adjusting status in the U.S. based on marriage, and your U.S. citizen spouse worked 40 quarters in the U.S. during your marriage, the support obligation is taken care of. Your spouse need not fill out Form I-864, but should instead fill out Form I-864W, explaining that they fall within an exception. Of course, it's rare for a married couple to have gone so many years (approximately ten) living in the United States legally without applying for a green card for the immigrant. Nevertheless, for those to whom this exception applies, it's highly useful.
The second major exception is that if the immigrant beneficiary is a child who will become a U.S. citizen immediately upon approval or entry to the U.S. for a green card, no I-864 needs to be submitted for the child. Once again, however, the petitioner should submit a Form I-864W to explain the situation.
Other family-based green card applicants who don't need to fill out Form I-864, and should instead fill out an I-864W, include self-petitioning widows or widowers of U.S. citizens and self-petitioning battered spouses or children.
If the U.S. family sponsor's income isn't high enough by itself to meet the Poverty Guidelines requirements, personal assets of the sponsor or the immigrant (or even the sponsor's household members) may also be used to supplement the sponsor's income.
For example, you could list such assets as real property (land or a house), bank account deposits, and personal property, such as automobiles or jewelry. The assets must be readily convertible to cash (for example, by selling them) within one year's time.
You don't get to count the assets at their full cash value for immigration purposes, however. In most cases, you must divide the value of the assets by five; or by three if the applicant is an immediate relative, for example the husband, wife, or parent of a U.S. citizen.
Income issues are the cause of many denials of green card applications. It's worth getting a lawyer's help to deal with this thorny issue.