In one of my old save, my sims house became a Nightclub even if they still live there and one the map, it seems they now posed it as business. It happened after they came back from the Magic Realm.
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Ideas
The house is from the gallery but for the rest, I can't remember, sorry.
There do seem several triggers.
My guess it's this issue: [WORKAROUND] Lot Types Change/ Business Funds for residential housing | EA Forums - 11456854 although your save doesn't have the business funds part but maybe that doesn't occur anymore.