I enjoyed working in a bank for years but I do not understand why a serial entrepreneur would enjoy it. After all, banks have lots of rules and procedures and formal hierarchies that squelch spontaneous action.

But on December 12 I spoke with a CEO who just signed the papers to sell his startup to a bank and he was ecstatic. And the reasons for his happiness suggest that there are important lessons to be learned from his experience about selling your startup.

The CEO in question is Tim DeMello, CEO of Boston-based Gradifi which has developed "a student loan paydown platform to solve the biggest problem millennials face -- $1.3 trillion worth of student loan debt."

Gradifi sells to companies -- PwC is a big client -- that help pay down employees' student loan debt in concert with employee contributions. Companies contribute directly -- through structured and secured channels -- towards their employees' student loan principal on a monthly basis. Companies pay Gradifi a monthly per-user fee.

On December 12, DeMello told me that he sold Gradifi to San Francisco-based private bank, First Republic, for an undisclosed amount on December 9.

As he explained to me in October, DeMello -- a trustee at Babson College where I teach strategy and entrepreneurship -- has been starting companies for the last 30 years before which he was a stockbroker.

DeMello got the idea for Gradifi in a Babson board meeting as he was listening to a discussion about student loans. He thought that students who typically borrow $35,000 could achieve a 25% reduction in their student loan payments if they could cut their monthly payment by $100.

Gradifi charges companies $3 to $5 per employee -- which is less than companies would pay to build and operate their own platform. But Gradifi's biggest benefit to companies is that it lets them outsource to an expert the process of making payments directly to employees in a secure, efficient, and scalable manner.

Since founding Gradifi in 2014, the company -- with 28 employees and $7.5 million in capital as of October -- had been on an aggressive growth trajectory. DeMello said Gradifi expected its service to be used by 10,000 employees by the end of 2016, 100,000 by the end of 2017, and 250,000 by the end of 2018.

The key to Gradifi's growth was its "inbound marketing" -- the ability to source new customers from its current ones -- especially PwC. DeMello said that in October Gradifi worked with 600 companies and was adding eight to 10 new ones each month.

Gradifi believes that it is going to be better off as part of First Republic. As DeMello said, "This is a great, sensational opportunity for the company to with a first class organization."

Since 2015, five companies expressed interest in acquiring Gradifi. DeMello passed on two of them in 2015 and met with three "in the last three months." First Republic was a Gradifi customer starting in August 2016 and "saw value in immediately." Gradifi and First Republic took six weeks to negotiate the deal whose purchase price is "undisclosed."

Why is DeMello so thrilled about this deal? Three reasons.

Independent Identity

If you sell your company, you want the acquirer to help you sustain the growth of the company you started. To be sure, some founders just want to cash out and leave. But the acquisitions that succeed keep the people who made the company successful.

DeMello believes it is very important for Gradifi to maintain its independent brand identity and First Republic agreed to do that. As DeMello said, "We wanted our own identity. And when we talked with customers, we found that they wanted us to have access to capital and other resources. With $65 billion First Republic, we get that. And founding CEO, Jim Herbert is a phenomenal guy. He is a partner I respect."

Indeed DeMello intends to stay with Gradifi and sees First Republic as a partner that will help him increase his staff "by 30% to 40% with no layoffs." This is a good sign that the deal may ultimately pass the integration test.

Happy Investors

When you sell your company, you want your investors to be enriched. After all, those investors bet money on your track record and you want to enhance your reputation with them.

DeMello says that the deal with First Republic further enriched his investors. "The deal has three components -- the first is an upfront buyout for all shareholders. Our angel investors earned returns between 72% and 212% annualized. For example, someone who put in $200,000 ended up with $800,000 after a year and a half," said DeMello.

This sounds to me like a win for those angel investors.

Greater Growth Potential

If your company has big growth ambitions, an acquisition can help you realize them only if you are targeting a big market and the acquirer provides capabilities that make it possible for the combined company to gain greater market share.

Gradifi believes that First Republic will provide the capital, excellent service, and national access to customers that it needs to achieve its growth goals. As DeMello explained, "We are targeting [a huge market of] Fortune 500-like organizations that wanted us [to add to our capabilities]. First Republic would provide access to capital and the ability to provide excellent service -- it has a phenomenal Net Promoter Score which on par with that of Apple and Amazon. First Republic has offices across the country and thousands of corporate employers as clients. And First Republic will invest millions in our business by 2019 and has given us an eight-year incentive program [that will reward us for achieving ambitious growth goals]."

This suggests to me that the combined companies have a good chance of being better off.

Gradifi offers a simple lesson: if you can find an acquirer that passes the four tests for successful acquisitions, you should do the deal.