BELOIT, Wis. — When Diane Hendricks sees something she doesn’t like here, she buys it.

A bankrupt country club. A half-empty mall. Abandoned buildings. The rusting foundry down by the river.

Beloit used to be a town that made papermaking machines and diesel engines. Ms. Hendricks thinks it can be a place where start-ups create the next billion-dollar idea, and she is remaking the town to fit her vision. She can do so because she is the second-richest self-made woman in the United States, behind only Marian Ilitch of Little Caesars Pizza, according to Forbes magazine.

“I see old buildings, and I see an opportunity for putting things in them,” says Ms. Hendricks, 70, who got her start fixing up houses here as a single mother and made her billions selling roofing felt, copper gutters and cement with her late husband, Ken.

Now Ms. Hendricks is fixing up Beloit.

She took the library from its historic location downtown and resurrected it inside a failing mall at the edge of town, replacing the original with a performing arts center where dance and music students from Beloit College can study and perform each year. Then she scooped up nearly every building on a downtown block and knocked each one down, making way for a sushi restaurant, a high-quality burger joint and modern apartments with marble countertops and exposed-brick walls.

Lyndon French for The New York Times

“It’s the one thing that Ken and I said we’d never do: buy restaurants or a golf course. And now we have both.”

Diane Hendricks, founder and chairwoman of ABC Supply.

She called the complex the Phoenix. “It looks like we’re beautifying the city, but we’re really beautifying the economy,” she says, casting her piercing blue eyes out of the window of her office in Ironworks, the old foundry complex she converted into a commercial space.

She has wooed several start-ups, persuading them to set up shop in the old foundry building — one with the help of Wisconsin’s governor, Scott Walker, who personally called the co-founders on her behalf.

Ms. Hendricks, a major Republican donor, was briefly thrust into the national spotlight a few years ago when she was recorded asking Mr. Walker to break up the labor unions. He then introduced a bill limiting the ability of public workers to bargain over wages. In response, protesters occupied the halls of the Capitol for weeks.

Not long ago, Beloit’s economy was ugly. Like many American cities — Detroit, Youngstown, Gary — it had fallen victim to the damage that is wrought when one major industry vanishes from town, reversing local fortunes.

Beloit is different today. That’s because this town of nearly 37,000 has a billionaire who has gone to great lengths to help it turn a corner.

In a nation with countless struggling towns and small cities, Beloit is not a model for economic revival that is easily replicated, although a few others have tried.

. . . .

Despite Ms. Hendricks’s efforts, unemployment is still high. A short drive south of the Phoenix and new buildings turn to boarded-up shops. Beloit remains deeply troubled. About a quarter of the population lives in poverty, twice the rate of residents in the rest of Rock County. One in every four children lives in poverty in the county, according to Project 16:49, a nonprofit group that works with homeless youth.

What’s more, many new jobs are filled by people who commute to Beloit from nearby cities. At AccuLynx, a software company based in the Ironworks, just 17 percent of the employees live in Beloit. The rest live in nearby towns in Wisconsin and just over the border in Illinois.

And many of the new jobs require technical skills, like engineering, that residents who once worked in manufacturing often lack. “I know that there are parts of Beloit that are not sharing in this renaissance,” says Scott Bierman, president of Beloit College.

Mr. Bierman credits Ms. Hendricks for providing a vision of how things can be. Still, he says, “I worry a lot.”

While he does see signs that what Ms. Hendricks has built can be sustainable, “We’ll know a lot more once we get through the next recession,” he said.

For now, around 1,000 people currently work out of Ironworks, according to Mr. Gerbitz of Hendricks Commercial Properties. “Our goal is to get to 5,000, which was what was lost when Beloit Corporation went away,” he said.

Ironworks today is a far cry from its foundry origins. At AccuLynx, the software firm, there is a giant slide running down from the second floor to the first, a video-game console and a giant gold bell that is rung when sales are made.

AccuLynx’s founder, Rich Spanton, described the day his grandfather, who had worked at the foundry as a superintendent for nearly a half-century, visited the building, where he had spent a career assembling steel parts for paper machines. He was astonished at what he saw.

“He walked in,” Mr. Spanton recalls, “and he said, ‘Jeez, we couldn’t have gotten any work done if this had been our office.’”