As I have posted earlier, we live in a multi-generational house. Mike and I, my mother, and our daughter are all living in the same house. There are a lot of benefits to this arrangement. We take care of each other, share expenses, look after each others animals, etc.
There are also some downsides. Mike would say the biggest one for him is he always has to be clothed. He is comfortable with my mom, but not comfortable enough to sit around the house in his underwear. This has led to some interesting outfits though! The other night he had just gotten a camo hat he had ordered in the mail from what I called "the ugly hat store". One of those "boonie" hats in the German camo pattern that he likes. So, he went into the kitchen wearing his new hat, his gray and black camo pajama pants and a red plaid button down shirt. He was certainly "stylin'! All mom could say was "nice outfit." (Mike hadn't expected anyone to be in the kitchen.)
Then, of course, there are the times when you have your mouth all set for something you left in the fridge only to find someone else got to it first. When the kids were younger Mike would write "Don't even think about it!" on food he put in the fridge. It rarely stopped them.
We also run into some issues with the thermostat! My mother is in her late 70's and has no fat left on her body since her last bout of cancer. To her, 80 degrees is chilly. We had to compromise on the living room temperature for the summer (78 degrees). Fortunately, and I recommend this to any family thinking about sharing a house with an elderly parent, we have zoned heating and air-conditioning. Mom has her zone, our daughter has hers and we have ours. Even now, mom is the only one who has had her heater running.
She and I went to the cabin this summer for a weekend together. It was raining and 70 degrees (which I find to be a delightful temperature in the middle of the summer!) She and I sat out on the deck for about 30 minutes and then she went inside, covered herself with an electric blanket and plugged in a space heater 2 feet from her chair! It took her 2 hours to "thaw out".
So if you are thinking about combining homes with elderly parents just remember to be ready to forgive, forget, and find the funny in everything!