This as-told-to essay is based on a conversation with Kathie Schwartz, 72, who built a tiny home in her California backyard. The conversation has been edited for length and clarity.

I wanted to get ahead of planning for old age. My husband and I are in our 70s and in very good health, but we’ve been losing friends and going to a lot of celebrations of life. At our age, that’s pretty common.

After one celebration of life, my husband looked at me and said, “Promise me you’ll never put me in a home.” That was kind of my jumping-off point: What were our options?

I started thinking about whether our home was still right for us and whether we were…