First thing in the morning, Allen Geiwitz goes to check on his mother, Hilda, who prefers to sleep in. He sets the breakfast cereal on the kitchen table, along with her pills. A little later, once she’s up, he goes back to fix her coffee.  “I’m there various times during the day to make sure she takes her medications,” said Mr. Geiwitz, 71, a retired computer programmer. “And she likes me just hanging around a bit.”  Mrs. Geiwitz, 95, no longer drives, so her son takes her to doctors’ appointments. He ensures that she has a steady supply of library books and nature videos. The two share dinner each evening with three elderly friends; Sunday evenings, they look forward to watching “Columbo” together on cable.  This vigilance, caregiving and companionship have become much simpler now that Mr. Geiwitz can look in on his mother just by walking down the hall. In 2014, he moved into Glen Meadows, the continuing care retirement community in suburban Baltimore that she had entered eight months earlier.  Now, each has a one-bedroom independent living apartment on the first floor.  Mr. Geiwitz often meets newcomers roughly his age who are scoping out the place for their parents. “They look at me strangely,” he said. “But to me, this is the future.”  You can see his reasoning. In yet another consequence of lengthening life spans, the adult children trying to care for people in their late 80s and 90s are likely to be approaching 70 themselves, or beyond it.  They may be wearying of housekeeping and home maintenance just at the point when their parents need more help. Caregivers over age 75 spend 34 hours a week assisting their elders, a study by the National Alliance for Caregiving and the AARP Public Policy Institute reported last year.  Across the country, about 1,925 continuing care retirement communities — in which residents can go from independent living to assisted living to a nursing home as their needs mount — house roughly 750,000 people, said Steve Maag, director of residential communities for LeadingAge, an industry association for nonprofit senior service providers. Eighty percent are nonprofits.  So far as he and other industry experts know, very few adult children have moved into their parents’ communities. “But it wouldn’t surprise me to see more of it,” he said. In less expensive regions, a continuing care community could offer a mix of proximity and privacy, and provide the greater levels of care that most older adults of both generations will eventually need.  “It’s remarkably common for children to make big adjustments to take care of an aging parent,” said Philip Sloane, co-director of the program on aging, disability and long-term care at the University of North Carolina at Chapel Hill. Sharing a continuing care community, he said via email, represents “a new but logical aging services model.” Where costs are reasonable, “it may well catch on,” he added.  A single man, he was already spending three to four days a week at his parents’ apartment. With assistance, his mother and father were able to prop each other up for years. But after her husband’s death, Mrs. Geiwitz, who has diabetic neuropathy and pulmonary disease and uses a walker, couldn’t manage on her own.  Mr. Geiwitz briefly considered moving into her apartment, but caring for a parent alone can become isolating and overwhelming.  So the family looked at several continuing care retirement communities, and Mrs. Geiwitz selected Glen Meadows, a nonprofit operated by Presbyterian Senior Living. Mr. Geiwitz paid the $35,000 entrance fee, half of it refundable when his mother moves out or dies.  That winter, “we had a 24-inch snowfall and then another 22 inches two days later,” recalled Mr. Geiwitz, who owned a house nearby. “I was old enough that just clearing off the car was a challenge.” Shoveling, mowing, raking, repairing — “either I was going to have to start paying people to do those things, or I’d have to sell the house and move into an apartment. I thought, ‘I’ll jump past that interim place.’”  He moved into Glen Meadows himself, paying a higher entrance fee, $88,000, all of which can be refunded when he moves out or dies.  The Geiwitzes will each pay $2,115 in monthly rent this year, which includes meals, activities, housecleaning, laundry and some transportation. Studio apartments cost less, semidetached patio homes more.  “Living here, I don’t have to do grocery shopping or meal preparation or mow the lawn,” Mr. Geiwitz said. “I can focus on what my mother needs and still have a life for myself.”  The community has walking paths and hiking trails he uses daily; he serves on committees that help maintain the grounds and oversee the art gallery.  He has friends because “I function well with older people,” he said. His next-door neighbor is a sharp 106-year-old.  “It makes it very homelike” to have her son nearby, Mrs. Geiwitz said. “It’s working out great.”  Many caregivers will find this solution unappealing. In an age-segregated society, few baby boomers welcome the prospect of facilities intended for old people, however lovely their campuses. In fact, LeadingAge announced last month that it would call C.C.R.C.s “life plan communities.” Focus groups had revealed that “the words ‘care’ and ‘retirement’ had a very negative connotation” to younger consumers, Mr. Maag said.  But the bigger barrier is probably economic.  These tiered communities usually require buy-in fees plus monthly fees, but contract types, refund policies and amenities all differ substantially. Moving in can cost less than $100,000 or many times that amount, depending on financial structures; whether monthly fees rise with higher levels of service, and by how much, also varies.  Geography matters, too. The well-run continuing care retirement community where my father spent his last months, in northern New Jersey, an expensive part of the world, doesn’t require buy-in beyond a one-time $1,500 “community fee.”  But two one-bedroom apartments there would now rent for more than $10,000 a month, making co-residence unaffordable to all but the very well-off.  In Waynesboro, Pa., however, entrance fees for one-bedroom independent living apartments at Quincy Village, another Presbyterian Senior Living community, range from $85,000 to $127,500 for one person, depending on the refund agreement. The monthly rent, $1,125, includes one meal each day, utilities and cable, activities, transportation and 14 days of nursing care each year.  Diane and Mike Matlock, both 67, moved into a two-bedroom cottage there in June. They, too, wanted to free themselves from home maintenance, especially after Mr. Matlock developed colon cancer and spent most of a year in treatment and recuperation.  “A wake-up call,” Mrs. Matlock said. “We had to make the decision to move sooner rather than later.”  They had visited Quincy Village often, because her mother lives there in a cottage that’s now a short walk from the Matlocks’ home instead of the previous hourlong drive.  Two other such dyads live in independent living cottages there: a 71-year-old daughter and her 95-year-old father, and another mother and son.  Mrs. Matlock’s 86-year-old mother, Nancy Gardner, remains quite independent. But Mrs. Matlock can drive her to medical appointments, drop off groceries, take her out to lunch. “It’s a real comfort to know she’s nearby if I need her,” Mrs. Gardner said. “And I try not to need her too often.”  For now, she doesn’t. But last winter the flu put Mrs. Gardner in a hospital for three days, followed by three days in the continuing care nursing unit.  “The older they get, the more you realize anything can happen,” her daughter said. “Now, I’m here if it does.”  A version of this article appears in print on January 5, 2016, on page D5 of the New York edition with the headline: A Move Into Mom’s Building. Order Reprints| Today's Paper|Subscribe
A few adult children have found that the simplest arrangement can be found in an apartment at the same retirement community.