FORTUNE — Josh Jarrett has spent a lot of time thinking about grit. It’s the entire premise of his startup, Koru. Alongside CEO and co-founder Kristen Hamilton, Koru seeks out recent college graduates who possess grit, or tenacity, or resilience, but lack real-world experience, and help them land jobs at fast-growing companies. Koru does that by through intensive four-week training programs, hosted at by the companies looking to recruit raw talent.

Through a filtering system, the company identifies job hunters who possess those qualities – the ability to take ownership, take initiative, and thrive in a fast-paced environment – and connects them with companies which are hiring. “High growth companies are looking at people who are street smart a well as book smart,” says Jarrett.

It made perfect sense, then, that this idea of grit and tenacity would appeal to the rapper Nas. “His background is the school of hard knocks in a certain way, and learning through experiences in life has gotten to him where he is,” Hamilton says. “He’s compelled by the way we’re preparing people to go to work.”

When Nas heard about Koru during the company’s $4.2 million Series A last December, he was excited enough to reach out and get involved. Now he’s putting his own money into the company, via his investment vehicle, Queensbridge Venture Partners. Beyond that, he’s decided to lend his time and star power, too.

Starting with the next class of trainees, Nas will offer ten scholarships to students (they cost $2750) to take Koru’s four-week program. He’ll also appear at a training session and offer advice and mentorship.

Koru is currently available in Seattle, but it will launch a program in San Francisco in September. The startup has worked with companies such as REI and Zulilly ZU , placing 63% of several hundred graduates into jobs. Koru makes money from its tuition, as well as through placement commissions from partner companies.

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Recruiting is a pain point for many high-growth companies, and a number of startups have sprung up to serve them. Companies struggle in particular with entry level workers who have no experience to highlight in their applications. “Hiring mistakes are expensive,” Hamilton says. “We realized a degree and GPA is not a good signal. We’re looking to be that signal.”

At the training programs, students do real project work within the companies. The idea is to help them develop hard skills around business, and personal skills around working with others. It may seem bizarre to outsiders that young people would pay a company to let them temporarily work for them, but Hamilton says skeptics come around once they see that Koru’s training is more valuable than an internship. “People quickly recognize they’ve been in school for four years and haven’t had a chance to even be in the arena where they’ll be working and expected to perform well,” she says. “People are starving for a way to get on the inside of a company.”

Nas isn’t the first celebrity to get involved with startups. Justin Beiber, Ashton Kutcher, Adrian Grenier, Oprah, Madonna, Ellen Degeneres, Z, Shakira, Will Smith, reality star Rob Durdek, and soccer star Gerard Pique have all invested startups, to varying degrees of success. Celebrity interest is an obvious indicator that there might be a startup bubble.

Not all of the investors mentioned above lend much beyond their name to the startups they back. But some want to get their hands dirty. That includes Nas, who has offered product feedback and promotional help where it makes sense, such as with Rap Genius, Crowdtilt, and now, Koru. Alongside his manager, Anthony Saleh, Nas has backed more than 40 startups, including Rap Genius, Crowdtilt, Coinbase, and Prism Skylabs. Most of the deals Nas participates in come to him through Andreessen Horowitz, who he met through Rap Genius.