Mary, if this gentleman has dementia, he may only be showing symptoms once or twice a week, but that will progress as time goes on, maybe slowly, over a period of years or maybe within just a few months. Everyone is different. Have you gone to a doctor or neurologist’s appointment with him? Do you know what type of dementia he has?
When his memory becomes worse and he can no longer remember things that happened yesterday or even a few hours ago, can you be comfortable with that? If and when he becomes incontinent will you be able to change him and dress and shower him when he can no longer do those things for himself?
You mentioned that your son financially supports you. Is he willing to support this gentleman as well if it gets to the point where you need in home care to help care for him? Medicare doesn’t pay for that. It’s self pay and is very expensive, even for a few hours a few times per week. If you were to get married would he be willing to give you power of attorney and put all of his investments in your name rather than in his children’s names so you can use that money for his care until that runs out?
Caring for someone with dementia is not an easy life. I agree with Larry’s advice of being close or very close friends with this man before tying the knot. After a couple of years you would be in a better position to make a decision.