We’ve been informed that a delinquent borrow left their house and moved somewhere else. The house we have mortgaged is no longer occupied. Are we required to wait 120 days to foreclose?

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.

Thank you for the reference! I really appreciate it!!