For many students, federal student loans don’t cover the cost of college. Purdue University is aiming to be a pioneer in a way to help students bridge that gap.

The government caps the debt available to most students at roughly $27,000 (total) for four years of school. Given that the average cost of a year of public school was $9,410 and $32,405 a year at a four-year private school last academic year, it makes sense that many families need to find more revenue sources to finance college. Some turn to private loans taken out in either a parent’s or the student’s name, and others take advantage of Parent PLUS loans, which is the government loan option for parents.

Purdue is experimenting with a new way for borrowers to supplement their federal loans: Allowing students to sell stock in themselves. The university will start accepting applications next month for its Back a Boiler program (the school’s students and alumni are called “Boilermakers”), which allows juniors and seniors to finance some of their education by pledging to pay back a portion of their salary over the next several years.

The school’s president, Mitch Daniels, described Purdue as “the national test bed” for these types of programs, known as income share agreements, or ISAs, as policy makers, researchers and higher education officials look for ways to make college more affordable.

“I’m very careful to say that we don’t know if this will have wings or not,” said Daniels, who is also a former Indiana governor. “It might be a superior option at least for some students and if so, let’s go see.”

Purdue’s idea isn’t totally novel, but it appears the West Lafayette, Ind., school is the first college to offer this type of program to students. There are non-profits who offer so-called income share agreements to students and in some countries, like Australia, the government deducts a portion of student loan borrowers’ income until the debt is paid off. Even Sen. Marco Rubio (R-Fl.) floated income-share agreements as part of his college affordability plan during his presidential campaign.

Purdue touts its program as a more affordable alternative than other options on the market, but Daniels notes that students should maximize their federal aid eligibility before signing up for an ISA.

In an example provided in a brochure for the program, the school claims that a rising senior who plans on majoring in history and wants $10,000 through an income-share agreement would pay 3.97% of their income for 9 years to pay it off. Students planning to major in a more lucrative field would devote a smaller portion of their income to paying off the debt because their projected income is higher. For example majoring mechanical engineering with a $10,000 ISA would pay 2.82% of their income until they pay it off, according to a calculator on Purdue’s site.

In both cases students would spend a bit more than $13,500 to pay off the loan, according to Purdue’s projections. That compares to a $17,124 total cost for a private student loan for $10,000 at a 9% interest rate, according to the brochure. Parent PLUS loans for this past academic year had an interest rate of 6.84%.

Daniels said it will take some time for the school to figure out exactly what percentage of income makes sense for each major. He’s hoping the number of students who sign up is in the mid triple digits and that they can collect multiple years of data to help figure out the terms of the agreement that make the most sense.

Proponents also note that income-share agreements offer better protection to borrowers from economic uncertainty because the borrower pays a percentage of their income. The ISAs can also be discharged in bankruptcy, something that’s nearly impossible to do with federal student loans.

“The student has a degree of safety here — if they go to grad school, if they become ill, the contract is suspended during that time,” Daniels said. “If things don’t work out even to the point of bankruptcy they’re in a much better position than in a traditional student loan.”

Still, the idea of asking students to pledge away a share of their future earnings strikes some as unseemly. Often proponents portray the programs as something different from a loan, but David Bergeron, a senior fellow at the Center for American Progress, a left-leaning think tank, said they essentially function as debt. “They start from a false premise which is this is free money, it’s money that has to be repaid if your income supports it,” he said.

And at this point, the agreements exist in relatively murky regulatory territory, so it may be hard for borrowers to get a true sense of the costs and benefits of the deal. A spokesperson at the Consumer Financial Protection Bureau wrote in an emailed statement that the agency, which oversees consumer lenders, is closely monitoring income-share agreements and the higher education finance space more broadly.

“It is important that consumers know upfront the costs and risks of financial products,” the statement reads. “This generally isn’t the case for income-sharing agreements, which can create challenges for borrowers trying to navigate their repayment options.”

Anthony Carnevale, the director of Georgetown’s Center for Education and the Workforce, said he thinks income-share agreements may likely be a better option for many families than Parent PLUS loans or other products. But he cautioned as with any financial product, “let the buyer beware.”

Wider uptake of these kinds of agreements could accelerate a turn away from students choosing to major in liberal arts or other low-paying majors, he said. Already, it’s more often the case that only wealthier students can afford to study fields that don’t directly translate into a career such as history or English.

“There’s a reality here that’s very difficult and that is that more and more college education is about what you’re going to make after college,” Carnevale said.

Bergeron, a former assistant secretary for postsecondary education, said he’s not necessarily against steering students toward programs that give them better outcomes, but he wonders if income share agreements that are more likely to benefit high earning majors may simply limit access to education to students who want to pursue a different degree. He said he’s wary of colleges offering another loan option in lieu of increased state support for higher education or more grant aid. Daniels framed the ISAs as part of a broader program at Purdue to make college more affordable, which includes freezing tuition.

Still, Bergeron said of ISAs, “all it does is provide an additional revenue stream for the institution over the long term. That seems to be doing something to benefit the institution and not really put the student first.”