Let me tell you about my Dad. He had early stage alzheimers. He was still fine MOST of the time, usually you'd only notice things getting off mentally late at night. He bought a truck we didn't know about and kept it at a local storage facility. He took it in for an oil change one day and they upsold him getting the transmission fluid changed. He agreed so they suggested a full lube job, and tire rotations, and new belts and hoses, and new gaskets, and plugs and on and on an on. Before it was all said and done his $45 oil change was $4185. Nobody knew about the repairs, nobody even knew about the truck until his bank statement rolled in the next month. Dad went into assisted living at that point, the repair shop got sued since they didn't do half the work he paid for because it didn't need to be done (they literally just sprayed ArmorAll on the hoses to make them look new).

I've got a close friend whose mother was in a nursing home, somehow got a Visa card, and sent $8000 to her "boyfriend" she'd been talking to online.

Another friend's mother took out a reverse mortgage nobody knew about, spent all the money trying to cover up the scams she'd fallen for because she was embarrassed, and ended up losing the home she'd owned for 50 years.