The Immigration and Naturalization Act (INA) already says that immigrants can't be a "public charge," meaning they aren't supposed to cost taxpayers money by relying on public benefit programs. If they are, or are likely to become, a public charge, immigrants are not eligible for visas or green cards.
The U.S. Citizenship and Immigration Services recently announced a significant policy change. In the past, when an application for a visa or lawful permanent resident status contained errors, the USCIS adjudicator would issue a Request for Evidence (RFE) or a Notice of Intent to Deny (NOID). This would notify the applicant of a deficiency in their application and give them a chance to address the problem before the application was officially denied.