Congressional Budget Office Cost Estimate: S. 1900: Emergency Supplemental Appropriations for Humanitarian Assistance and Security at the Southern Border Act, 2019 [open pdf - 80KB]
From the Document: "S. 1900 would provide supplemental appropriations for fiscal year 2019 to expand federal agencies' capacity to respond to the large number of foreign nationals attempting to enter the United States through the southern border and to provide humanitarian assistance--including food, shelter, and medical services--to such individuals. The bill would designate those amounts as emergency requirements pursuant to section 251 of the Balanced Budget and Emergency Deficit Control Act of 1985. The limits on discretionary budget authority established by the Budget Control Act of 2011 (P.L. 112-25), as amended, would be adjusted to accommodate the funding"
Congressional Budget Office: http://cbo.gov