While Dominican nuns are not generally in the business of acquiring nightclubs, the inquiry made sense to those who know Sister Christina.

After all, over the last two decades, Heltsley, who runs the St. Francis Center, has become the go-to buyer of property in North Fair Oaks, an unincorporated, mostly Mexican immigrant enclave of 15,000 in San Mateo County that is squeezed between Redwood City, Menlo Park and Atherton.

Using private money from families and foundations, Heltsley has bought 17 properties and turned the collection of once dilapidated real estate into a tight-knit community with a school, youth recreation center, food pantry, clothing program and 259 deeply affordable apartments spread out over 15 buildings.

Blocks once controlled by Norteños gang members dealing meth had become tranquil. Junkyards that had served as venues to strip and set ablaze stolen cars were transformed into community gardens where North Fair Oaks families grow produce and flowers.

Still, the idea of buying the Hanky Panky — a single-story concrete box on El Camino Real — was a bit much. “There was not enough sage and incense in the world for me to buy that,” Heltsley joked.

Now, Heltsley has a new project: a 40-unit, ground-up modular project that will bring the total of St. Francis Center’s low-income housing portfolio to nearly 300 units. It will cost about $20 million — she hasn’t started raising funds yet and will be one of the more ambitious projects that the center has taken on.

“We don’t have a choice,” she said. “The need is huge. I want to be able to densify the community without ruining the community feel.”

To step into the St. Francis Center — a block from the old Hanky Panky — is to enter into a wood and plaster manifestation of Heltsley’s vision for what a thriving, low-income immigrant neighborhood could be.

On the ground floor, volunteers sort bags of clothes — they “rehome” about 35,000 bags a year — while a crew in the food pantry assembles boxes of produce, dairy, meat and canned goods. The facility also has a shower and washer-dryer setup for unhoused neighbors.

Upstairs is home to the Holy Name School, a K-8 school which serves two classes of 16 at a time. For instance, this year, there is a kindergarten class and a sixth grade class. While the families — mostly immigrants from Mexico — do not pay any tuition, at least one parent is required to spend one day a week at the St. Francis Center, where they receive English tutoring from volunteers.

If the upstairs feels like a well-appointed home in Atherton —  with oriental carpets, antiques, wide-plank oak floors and well-mannered dogs named Tinsley and Grace — it’s because that is how Heltsley wanted it.

“We try to make it homey. Even the dogs are purposeful. They roam in and out of the classroom and the kids can de-stress with them,” she said.

Raised in Pasadena as one of nine kids in an Irish-Catholic family, Heltsley was not on the track to become a nun until after college. Just before graduating from UC Santa Barbara she came across a flyer advertising a program for volunteers to teach at inner-city communities. She moved to Chicago and ended up living in a convent and teaching at the school next door. Soon enough, she joined the fold.

“I was like a duck to water,” she said. “I knew that was what I was meant to do.”

After 18 years of teaching and serving the poor in the Midwest, Heltsley returned to California, first as a doctoral student at the University of San Francisco and later as the superintendent of a Catholic school district in Monterey. But, she felt hemmed in running a large bureaucracy and in 2000 jumped at a chance to take over the tiny St. Francis Center, which, at the time, consisted of a single two-bedroom bungalow with just a food pantry and clothing exchange.

Within a few years Heltsley, who lived in one of the bedrooms, had founded the school, started buying run down apartment buildings and renovating them from the studs up. She built the Siena Youth Center, which has a full-size gym, homework rooms, industrial kitchen, digital arts center and a bike repair program.

The youth center, which opened 10 years ago, was a threat to the gangs, which had a tight grip on the neighborhood and were accustomed to recruiting children as young as third grade. Soon after opening, a gang fight broke out in front of the center and Heltsley went outside to call the police. She was attacked by one of the gang members who smashed her phone on the sidewalk.

“One of the gang members said, ‘We don’t call the police in this neighborhood,’ ” she recalled. “I said ‘I do.’ ”

San Mateo Sheriff Christina Corpus, who spent years working as a community officer in North Fair Oaks, met Sister Christina in 2008. “Everyone calls her ‘Sister Saint,’ ” Corpus said. “She has tenacity, grit and a lot of compassion for the community.”

Corpus and Heltsley worked together to establish a satellite sheriff’s office in the youth center, in order to make kids more comfortable with law enforcement.

“We had a lot of violence in that neighborhood, a lot of drug trafficking. She has really transformed that community to feel more like a neighborhood where kids are comfortable playing outside.”

In the world of affordable housing, the St. Francis Center is unique in that it doesn’t use public money or tax credits.

“Government funding slows everything down — I don’t have the time,” Heltsley said. “The need is so great we need to act nimbly. We need to be able to take down a property, rehab it and turn it into low-income housing.”

Instead, Heltsley has cultivated a community of passionate supporters that include some of the Peninsula’s wealthiest families, including billionaire real estate developers John and Sue Sobrato; philanthropists and former San Francisco Giants owners Bob and Connie Lurie; and Ned Spieker, founder of Spieker Properties, one of the largest commercial real estate owners in the U.S.

“I could never ask for money for myself — I would die of embarrassment — but I have no qualms about asking for this community, because the need is real,” Heltsley said.

Unlike large nonprofits or housing developers with thousands of units, the St. Francis Center is geographically focused and its impact is clear to anyone who walks around North Fair Oaks.

“Donors can see their money in action,” Heltsley said. “And they know this middle-class girl does not waste a cent.”

The whole family approach has transformed the life of Lulu Barajas, who arrived in North Fair Oaks at age 17 from Michoacan, a state in western Mexico that many North Fair Oaks residents have immigrated from.

She learned English at the St. Francis Center while her kids were in school there and her kids — like almost all the graduates of Holy Name — end up with full scholarships to Catholic high schools on the Peninsula. One of her kids graduated from San Francisco State with a degree in psychology. The middle one is at Sacred Heart Prep and the youngest is still at Holy Name.

Barajas is now a property manager for the nonprofit, overseeing 50 units, and studying early childhood development at Cañada College.

“Sister Christina is part of my family — she basically raised me,” said Barajas. “She always says I’m her crazy adopted daughter.”

Everyone has a story about how they met Sister Christina.

Bill Butler, CEO of W.L. Butler Construction, said he met her at the posh Sharon Heights Golf and Country Club in Menlo Park. Heltsley was having lunch with U.S. Rep. Anna Eshoo as well as another friend and, before he knew it, the nun had persuaded him to become St. Francis Center’s general contractor.

“She is like a whale fisherman. She drags you in. She is a heck of a nun,” Butler said. “She just drives around this community and when she sees a dumpy old building, she finds out who owns it and sees if they will donate it. Usually they won’t, so she’ll start dialing people up.”

Philanthropist Connie Lurie said she met Heltsley at the request of Atherton Police Chief Steven McCulley. “The chief said, ‘I want you to go over and meet sister Christina,’ ” Lurie recalled. “I said, ‘First of all I don’t live in Redwood City and, second of all, I’m not Catholic. Why do I have to go over and meet her?’ He said, ‘Just go.’ ”

Lurie said she was taken with the St. Francis Center’s holistic approach: the community gardens, the youth center, the fact that parents are also required to be students.

“Nobody else does that,” Lurie said. “She is just so creative and thoughtful.”