RESPA wouldn't require it. Not sure about any state law/contract issues.
1024.30(c)(2) - Comment 1
1. Principal residence. If a property ceases to be a borrower's principal residence, the procedures set forth in §§ 1024.39 through 1024.41 do not apply to a mortgage loan secured by that property. Determination of principal residence status will depend on the specific facts and circumstances regarding the property and applicable State law. For example, a vacant property may still be a borrower's principal residence.