Ironically, the misuse of “premise” to mean a dwelling or habitation is based on an erroneous premise: One house, two houses; one business, two businesses. But there is no singular of “premises” when it refers to land and buildings.
The word “premise,” meaning “a proposition that supports a conclusion,” can be plural—“premises.”
Both words probably have the same Latin root—“what comes before.” The proposition comes before the conclusion, clearly. In the case of the land and buildings, deeds and title documents used the word “premises” to avoid repeating the full legal description. “Premises” just meant “that place we’re talking about.”
If you hear someone using “premise” as a singular for anything other than a logical proposition, just order them off the premises.