I have 3 elderly friends/neighbors I've adopted like that. They all still live in their homes and maintain their large properties. One is 90, one is 93 and one is 99. The 93 & 99 year old still drive! 
with no issues. I love hearing all the stories and drinking wine with my WWII war bud.
I have a few elderly friends like that as well. It's really such a special relationship, that unless someone has shared or experienced something like this, they rarely are able to understand how mutually rewarding it is.
I can't tell you how beneficial it is to learn from others who have "been there, done that". They have sooo much knowledge, wisdom, and life experience, and being able to share it with others is so rewarding for them as well; emotionally & mentally, it keeps them young, ...especially when "viewing life through the eyes of a child."
Last month I was working on a DIY project, and discovered I didn't have the right tool, so I found my way to my elderly neighbour's house to see if I could borrow the right tool. We started discussing my project, ...and the next thing you know, I see his eyes light up, as he decides to start a business marketing my little project, building them from his little workshop.
