As the child of a divorced, unemployed mother, Shira Eisenberg learned to get by, she says, “on the kindness of strangers.” But even she was surprised when she arrived at the University of Chicago and was told that if she jumped through a few hoops, like going to seminars on how to behave at a job interview, she would be guaranteed a paid internship, financed by the university if no other source of money was available.

“Without the stipend, I would not have been able to afford it,” said Ms. Eisenberg, a sophomore majoring in computer science and minoring in neuroscience.

Internships have become a necessary credential in a highly competitive job market — about half of interns are offered a job by a company where they have interned, according to a 2017 survey by the National Association of Colleges and Employers.

But for those thinking of careers in nonprofits, public service, social services or the arts, paid opportunities are scarce. Employers often can’t afford a stipend, and many students can’t afford to work for free.

In response, campuses are using philanthropy and their own funds to subsidize internships at organizations that have a mission of social change or innovation. Students can pursue their passion without worry about how they will pay for food and housing, and for those who see Goldman Sachs in their future, it’s a chance to do good works.

“We don’t want our students to pick a field because it pays and overlook another field because it doesn’t pay for an internship,” said Meredith Daw, executive director of career advancement at the University of Chicago.

There are 2,000 placements each year through Chicago’s Jeff Metcalf Internship Program. Employers agree to cover the salary — at least $11 an hour or the local minimum wage, whichever is higher. But when an organization can’t afford to pay — 40 percent can’t — the university provides a $4,000 grant for a 10-week stint.

Starting last year, the university’s Odyssey Scholars — low-income students like Ms. Eisenberg — have been guaranteed a paid internship for their first summer. That, Ms. Daw said, is when they are at the greatest disadvantage compared to their peers with more of the social capital — like parental connections — needed to find internships on their own. Last summer, 232 students participated.

Ms. Eisenberg interned at the Centers for Disease Control and Prevention in Atlanta, where she developed a machine learning model for its library. The grant helped defray airfare, her summer sublet and other expenses.

Pace University posted more than 4,000 internships last year, about 40 percent of them unpaid, and provides grants for many internships in the nonprofit sector.

“We’re not trying to proselytize with these students, but we’d like their eyes to be open to the second and third sectors in our economy,” said Rebecca Tekula, executive director of Pace’s Wilson Center for Social Entrepreneurship. The center pairs students with nonprofits in and around New York City, like Greyston Bakery, Housing Works and the Legal Aid Society. Elizabeth Pooran interned last year at Senior Planet Exploration Center in Chelsea, a community space designed to teach technology, including digital photography and the internet, to older adults to encourage them to lead independent, connected lives. And Latino U College Access, a fledgling nonprofit that works with first-generation college students, has used Pace interns for three of its five years. “I always say that my organization was built with the support and by the hands of Pace University interns,” said Shirley Acevedo Buontempo, the founder.

Students in the Wilson internship program receive $16 an hour, or $4,480 for eight weeks. Some 120 students have participated since 2009, with grants totaling about $500,000.

Macalester College, too, subsidizes internships involving social missions, like helping integrate tuberculosis services into Georgia’s health system and fighting transgender discrimination. Last year, about 50 interns took part.

“This is an opportunity to try on a career no matter what their interest or major or their economic situation is,” said Mindy Deardurff, dean of career development at the St. Paul campus. “Especially for our students who have socioeconomic need, if we can get them in and let them try out some of the things they are so passionate about, it might get them over that hump of worrying about whether they can afford it.”

Amherst College distributed $1 million this past summer, 40 percent more than it did the previous year, helping 229 students take unpaid internships with nonprofit organizations and small start-ups. The money came from alumni gifts and $200,000 from the Jack Kent Cooke Foundation, which supports low-income college students.

Because more than 80 percent of Amherst students go to graduate or professional school, some of the money is used to prepare them by financing research internships, study abroad and independently devised programs, said Emily C. Griffen, director of Amherst’s Loeb Center for Career Exploration and Planning.

Michael Loeb, president and chief executive of Loeb Enterprises, is an alumnus who has taken a particular interest in internships. In addition to offering paid stints at his own company, he has just started a program that matches start-ups in New York City with Amherst interns and covers their pay and living expenses.

It’s not surprising that alumni favor their alma mater.

Over the past five years, alumni and parents have donated $4 million to Colgate University, enabling it to support some 200 students each year who want to take unpaid or low-paid internships, typically with nonprofits, the creative arts or to do research. Last summer, it spent $666,000, said Michael Sciola, associate vice president of institutional advancement and career initiatives. Colgate students can also come up with their own grant proposal, and the university will help them find a host who will turn that into an internship.

“We do allow students to do a self-designed summer,” he said. For example, twin brothers received a grant to pay for travel to work on an archaeological expedition in Alaska.

Mr. Sciola concedes that the connection between “an immersive experience” and a career might be less obvious than with an internship in the financial industry. That’s why students are more likely to take less career-driven internships in their first and second years, he said, when they are still exploring.

“Our overall goal is to empower our students to explore their interests with practical immersive experiences,” he said, “without the limitation of financial barriers.”