"chronically ill" can mean anything
Yes, I am chronically ill. I understand that it is rather unusual to plan for a later disability at this age. However, since I haven't been able to leave my apartment for several weeks and my illness is quite unpredictable, I would prefer it that way.
Tightness, whether too steep roof slopes or too narrow access points, e.g. in the kitchen or bathroom, or stairs resulting from insufficient space, are already a challenge for a healthy person. In addition, you probably still have the courtesy distance, which does not exist among couples or married partners, making everyday life in a small space somewhat easier. If you, as a chronically ill person who is sometimes simply much less mobile than healthy people for longer periods, make concessions regarding the house, and then also mention that everything (decisions) depends on one person, then are you in a voluntary financial dependency relationship? Honestly, I cannot weigh at all what is right, what one could/should advise, or whether one can even put oneself in that position. From an outside perspective, I do not see you in an attic room, nor building a house where you cannot have your room on the ground floor.