It can also happen quickly with isolated parents if they're at a transition point (still living home) and a scammer walks in. I had a friend who's father was starting to suffer from dementia and had a woman who got control of some of his bank account info and was emptying him out. After my friend had his dad hospitalized, she was calling the hospital trying to get access to him and he had to get his room changed to an alias. Hospitals have frighteningly poor security measures.