“Skid Row is sad,” Ms. Welker said. “It is as sad as you can imagine. You literally have to live here to see how sad it is.”

Ms. Welker, chatty with a wide smile and white flowing hair that falls over her shoulders, has her routines. She knows the staggered schedules of the soup kitchens. Her bad leg and wheelchair usually entitle her to a spot at the front of the line, and she brings a plastic baggie to collect extra food to pass on to friends on the streets, or to eat when she returns to her room.

She passes the days riding her wheelchair, waiting for the battery to run down so she can return to her room and charge it up for the next day.

“You have to wait until it goes down to two or three dots,” she said, flicking her finger at the battery indicator. “So I just ride up and down the street and say ‘hi’ to everybody. And when my chair goes down enough, I go back in. I have to charge my chair. And I have to elevate my leg, otherwise I could end up losing it.”

The challenges faced by people like Ms. Welker have forced advocates for the homeless and government agencies to reconsider what kinds of services they need: It is not just a meal, a roof and rehabilitation anymore.

“The programs for baby boomers are designed to address longstanding programs — mental health, substance abuse,” said Benjamin Henwood, an assistant professor at the University of Southern California School of Social Work. “But they are not designed to address the problems of aging, and that is a big problem for homeless treatment in the years ahead.”