My Dad is like that. He'll ask for a little help and before you know it he has consumed my every Saturday for a month. A few years ago I just flat told him he can't be doing that. It was part of a larger conversation in which he was trying to blame my wife for driving us apart. (She's been a saint about the whole thing. She keeps saying, "When he's gone you'll wish he was still coming around.") Anyway, I told him that if he's going to come over to my house and call my wife evil, he can just stay away. He got his pride all up in a knot and said fine (with that look on his face that I have known since I was a little kid...) and off he went. It took us a year or so to get it patched up but our relationship is much better now.
Dad lives in his camper and hauls a Geo Metro on the back of his truck. He comes around some, but for a guy with all his time to fill and little to do, he shows remarkable restraint. He will ask me to work on things yet, but he gets a lot more done on his own, by finding a retired welder here and a shade tree mechanic there. After all, he has nothing to do but spend his time hunting these people down. With his VA disability, free medical and no taxes he makes more money than I do, so I don't feel guilty making him spend a little of it.
He spends every winter down south, and I keep thinking that one of these years I'm going to have to go collect him. It'll be a sad day.
My mother in law is widowed and still living in her home place. She asks for very little, but all I have to do is look around and I can find all kinds of things to do there. She has had some problems, and I am afraid that if we make her move into a senior apartment in town she will lose her frame of reference and just give up. She is 6 hours away, but we keep spending our vacations going up there and doing what we can. My sister in law and her husband are closer, so they do a lot more than we do.