Hi "Mom," and that you for writing.
Manufactured homes come in two guises. They are either real estate -- on a permanent foundation, at least a double wide, and you pay real estate taxes on them. Or they are personal property, can be on wheels and can be single wide. Your financing depends on which of these homes you're considering. I am assuming from your question that this home qualifies as real estate. See USDA here for detailed requirements. https://www.rd.usda.gov/files/RD-SFH-ManufacturedHousing2.pdf
According to the USDA, "Sec. 3555.208 Special requirements for manufactured homes. Loans may be guaranteed for manufactured homes if all the requirements in this section are met."
And here are those requirements:
Rural Development may guarantee a loan used for the following purposes related to manufactured homes when a real estate mortgage covers both the unit and the site:
(1) Purchase of a new manufactured home, transportation, permanent foundation, and installation costs of the manufactured home, and purchase of an eligible site if not already owned by the applicant; and
(2) Site development work properly completed to HUD, state and local government standards, as well as the manufacturer’s requirements for installation on a permanent foundation.
The USDA does not pick the site - YOU do. It either goes on land that the developer sells you or on land that you purchase, or on land that you already own. But the agency does not tell you where to put the house. Good luck and than you for your question.