Jay Miles has lived his 52 years without marriage or children, which has suited his creative ambitions as a videographer in Connecticut and, he said, his mix of “independence and stubbornness.” But he worries about who will take care of him as he gets older.

Donna Selman, a 55-year-old college professor in Illinois, is mostly grateful to be single, she said, because her mother and aunts never had the financial and emotional autonomy that she enjoys.

Mary Felder, 65, raised her children, now grown, in her row house in Philadelphia. Her home has plenty of space for one person, but upkeep is expensive on the century-old house.