You both should take a really hard look at how much care you’re going to be able to provide to them, and how much you actually want to do. It is not easy. My mom got brain damage/dementia from an illness when I was 18, and I lived with my parents for 15 years, from age 22-37 to help my dad take care of her. Right after I moved out, my dad was diagnosed with a terminal illness. They moved into independent living for the last two years of his life, and paid for extra care for their needs. At the time, we didn’t have a full grasp on the finances, or Medicaid eligibility, so when my dad died, my husband and I moved her in with us. My mom was relatively easy to care for, she is not combative, can feed herself (but not cook), can mostly dress herself, and we kept her occupied with coloring books while we worked at home. As long as there were no bathroom issues, and she got enough sleep/wasn’t sick, it wasn’t that hard, so on the surface, we should have been able to do it forever. But she can’t be left alone, we had to use a service to come stay with her when we needed a night off, or went on vacation ($35 an hour, with a 12 hour a week min if you booked coverage for the week). My husband and I never went to the grocery store together while she lived with us. It was always you take care of this, and I’ll go do that. There was no spontaneity, our entire lives were planned weeks in advance. If one of us had to travel for work it made a long week for the other person. Bathroom accidents were very hard. You can’t just pick up a 140 lb woman and put her in the bath. And she seemed to always have major diarrhea right before something important, which caused us to scramble. When she caught Covid, we learned that she can’t walk if she has a fever. I spent several nights sleeping on the couch with her sleeping in a recliner so that I could assist with going to the bathroom when her legs weren’t strong due to fever or lack of sleep. My husband developed anger issues and I suffered from anxiety. After 19 months we could no longer do it. She now lives in assisted living with memory care support and she’s doing ok. It’s a nice place, with plenty of activities every day, it’s not a nursing home. I’ve spent my entire adulthood caring for my mom in some capacity, and I just couldn’t give up any more of my own life doing it. I still handle all her finances, and admin needs, I still take her to appointments, and I visit regularly. But your idea, even with separate buildings or entrances is not something I’d ever consider doing after living through all of this.

All of that said, if your husband doesn’t have durable POA for finances and medical for his parents, that should happen soon. It will be much easier down the road if he’s able to assist with decisions.