Mahjong, affordable groceries, and shared community space are vital for the thousands of senior citizens living in San Francisco’s Chinatown.

San Francisco population is the oldest of any major American city, with official data showing that 21 percent of people there are aged 62 or above. And that's particularly true of the one-in-five San Franciscans who are Chinese-American, according to Jennifer Chan from the Chinatown Community Development Centre.

Chan's organisation provides subsidised homes for elderly people, who must have a monthly income of no more than US$2,100. Tenants pay no more than a third of their income in rent, with the government paying the rest. She says supply seriously outstrips demand, with applicants waiting at least five years for a home.

“Senior affordable housing is actually very much needed in San Francisco. Housing is very expensive here. Our wait list here has a couple thousand people on it. We only have 103 units here. And so, you can imagine that most seniors only move out when they pass away, so you often don't see a lot of vacancies in a building like this,” she said.

The real estate agency Zillow lists the average price of a studio flat in San Francisco as US$2,150, so it's little wonder that one tenant, Lau, compared getting a subsidised home to “winning the lottery”.

Like many Chinese immigrants, Lau said Chinatown’s network and cheap housing make it an ideal place to stay.

“I play mahjong with a few elderly friends for around four hours [every day]. Sometimes my son comes and brings me a big bag of figs. Then I will share them with my neighbours or make soup for them,” he said.

Chan said building a co-living space is crucial for fostering a sense of community.

“It's very important, not just for seniors but for the families that they come and visit, and the vitality of the community," Chan said.

"Having a place where residents can go out and speak their home language to be able to access groceries, medical needs, any of that, and just be able to walk home and do that. It's very important for the vitality of Chinatown.”