It was the humble, reliable rowhouses that drew Anita Flynn to Mayfair in 1985, and the ease of commuting to Center City.

Homes there were relatively affordable back then. Crime was infrequent. Mayfair was at the center of a blue-collar swath, the kind of place where neighbors took care of neighbors.

So Flynn purchased a three-bedroom home for $54,000. She raised a child and buried a husband, attended block parties, and cared for her lawn. Her neighbors stepped up when she could not, babysitting and helping after her husband died.

Yet today, Flynn said, she hardly recognizes her neighborhood. Once populated by homeowners, Mayfair has experienced one of the region's most significant drops in that category. Renters have moved in. Petty crime is up. And her community has nearly evaporated.

"I'm sitting on a block where I don't know as many people," said Flynn, who is retired from customer service. "More are planning to move. So where does that leave me? I don't want to be the one left behind."

Now 60 — too young to need to worry where she will live in the future, but old enough to start planning — Flynn already recognizes a problem: Though paid off, her aging, multilevel home will not be suitable. And as a middle-income senior, she is realizing, finding an appropriate and affordable alternative could be a serious challenge.

It's a dilemma arising nationwide as demographics and housing preferences are changing. Americans are living and staying healthier longer, and seniors consistently want to stay in their own homes. Yet many U.S. houses are ill-equipped for older occupants: too many steps, inconveniently situated bathrooms, and doorways that are too narrow. At least half of Philadelphia's housing is estimated to be more than 60 years old, and a substantial number of suburban homes are older, too. For many seniors, that means finding other options.

Plenty abound: retirement and 55-plus complexes; assisted-living facilities; nursing homes; memory or respite care. Yet with one-third of adults 50 and older considered "cost-burdened" because they pay 30 percent of their income on housing, and with almost a quarter paying more than 50 percent for shelter, affordable-housing advocates argue that immense challenges exist.

"Many people in their 50s and 60s simply lack the resources to obtain appropriate housing and services as they age," according to a 2014 report by the Joint Center for Housing Studies at Harvard University. "Middle-income adults may discover that long-term care insurance and senior housing communities ... are too expensive."

"Low-income households have even more limited options," the report continued. "... It is critical that the public and private sectors take steps to support cost-effective options."

Compared to the nation, Philadelphia lags in construction of new senior housing, according to the National Investment Center for Seniors Housing & Care, a nonprofit advocacy group. Across the U.S., NIC found, new construction in fourth quarter 2016 represented 5.7 percent of all senior-housing inventory — creating concerns in some markets of potential oversupply. In Philadelphia's metro area, that number was just 1.2 percent — even while Pennsylvania has the country's fourth-highest share of seniors.

"That means there's less development activity in the Philadelphia area," said Beth Mace, chief economist at NIC, which defines "senior housing" as including some independent-living communities — places like Brightview Senior Living in East Norriton and Mount Laurel — as well as assisted-living and memory-care facilities.

"The Northeast tends to have a more congested market ... more regulatory barriers to entry. The land that there is to develop is competing with a lot of other potential uses," Mace said. "A developer could build senior housing, or an apartment, or mixed-use. You have to have a compelling investment return to favor senior housing over a different property type."

Sluggish new supply has pushed local occupancy rates slightly higher here than the rest of the country, NIC says. And senior-housing rents remain higher, too. In Philadelphia, she said, rents average about $3,800 per month, or $46,000 per year — which can include meals, laundry and more. Nationwide, it's about $45,000.

For seniors like Flynn, the thought of absorbing that cost can be unsettling. "I'm thinking: 'Here we go again, do I really want another rent or mortgage?' " she said. "I really hadn't planned on starting over at 60."

According to some observers, senior-housing concerns can fall disproportionately on the middle class. More options exist for wealthier residents, they say, and for lower-income seniors who qualify for subsidies.

Yet low-income seniors often fail to secure assistance they need, the Harvard study found: In 2011, 3.9 million households 62 and older had "very low" incomes — at or below 50 percent of the area median. Only 1.4 million, or  36 percent, benefited from rental assistance.

To combat financial burdens and to allow more seniors to stay at home, government and nonprofit organizations can provide help. For example, the City of Philadelphia will "freeze" real estate taxes for eligible seniors who meet certain requirements. (One group: Adults over 65 who make less than $23,500.) The Longtime Owner Occupants Program provides a tax discount to seniors who have lived in their homes more than 10 years and have seen their property assessments triple.

Nonprofits have also filled in gaps: The Philadelphia Corporation for Aging provides minor home repairs, such as installing deadbolts, through its Senior Housing Assistance Repair Program. The Philadelphia Housing Development Corp.'s Adaptive Modifications Program can help permanently disabled residents stay at home by widening doorways or installing lifts, for example.

At the higher end of the income spectrum, a surge of new 55-plus developments and continuing-care retirement communities have boosted the number of options for those who can afford them, enticing seniors with tennis courts, pools, clubhouses, and more.

Sam Ballam, 66, and wife Susan, 64, were drawn to Athertyn in Haverford because of such amenities, plus features inside: an elevator; wide doorways; and extra bedrooms, should they eventually need a live-in nurse.

"It's like 60-year-olds moving into the freshman dorms," Ballam said of Athertyn, developed by Pohlig Builders. "You have this great network of people ... we didn't anticipate or think about that."

Communities like Athertyn can cost a chunk of change. Homes there are priced about $500,000 to $1.3 million, for about 1,800 to 3,000 square feet.

Still, according to a 2014 AARP survey, 87 percent of seniors would prefer to age in their own homes. Some renovate. Others build new.

Patrick Francher, 65, and wife Donna, 61, built an accessible house in Swarthmore two years ago, complete with elevator, where they hope to stay for decades.

"I understand seniors looking for a built-in sense of community," Patrick Francher said. "But we have a wide circle of friends here ... we created that community."