We had a wake-up call on the importance of this kind of stuff when my FIL was stricken with a form of ALS.
They were able to fit the home with wheelchair accessable ramps but the house was built during the time that it was fashionable to squeeze the bathroom into as small a space as they could. Made for an impossible situation for him.
When we built this house we also had a smaller bathroom; but it was larger than the in-law's was. We also thought it would be elegant to have a stepped living room. At the time we were building, dad told us; "Flat floors are good." Of course, we ignored him. The ALS deal changed our views on dad's advice. About 10 years ago, I redid the living room to get rid of the fancy step. Last winter, we redid the bathroom to conform to the ADA. I sure hope that aspect of it is a big waste of money.