In fact, with help from private equity, owners of plumbing and HVAC businesses can even fetch tens of millions of dollars.

“Sometimes I’ll literally say, ‘I make millionaires for a living,'” Redwood Services founder and CEO Richard Lewis said.

In an interview with Fortune, he estimated his company has minted more than 30 millionaires since he started Redwood four years ago.

Redwood, which is backed by the Union Main Group private-equity firm, specializes in acquiring residential plumbing and HVAC businesses around the country and partnering with their owners to accelerate growth. 

Lewis attributes his firm’s success to its business model of finding entrepreneurs in the trades who still have “gas in the tank” to keep working but have hit a growth ceiling and need some help getting to the next level.

That’s where Redwood comes in. Not only does it provide capital to business owners to add employees and equipment, it also offers help with things like coaching, marketing, accounting, software, and negotiating with suppliers.

“Day one, we are upgrading fleet, we’re buying fleet, we’re investing in managerial talent,” Redwood Chairman Adam Hanover said. 

Deals have ranged from $400,000 to $50 million. Smaller “tuck-ins” are typically around $1 million and involve a 100% acquisition. Those businesses have 5-20 employees.

Meanwhile, deals for bigger firms that employ 75-100 people have valuations averaging around $20 million. Redwood gets a 75% stake in its new “partner” business, and the original owner keeps 25%.

In contrast, other models usually involve full takeovers where the original owner hands the keys to the new PE buyer and steps aside from the business.

But for Redwood, that 25% stake is critical—for both sides of the deal. Indeed, Lewis insists the owners keep some skin in the game and believes this ownership model makes Redwood stand out from its competitors.

“You own 25% of your entity, and that means you are incented to work your ass off and to really help us grow this business,” he explained. “Because that 25% that you own could very well be worth more than the 75% that you sold us up front.”

That’s the case for half of Redwood’s 16 partner firms, as the estimated value of the minority stake now exceeds the amount paid for the majority share, according to Lewis.

“There is real financial life-changing generational wealth opportunity that is created with the 25% equity that they are rolling into this partnership with Redwood,” he added.

Lewis said he loves making millionaires for a living because the business owners he partners with aren’t “silver spoon people.”

Instead, they’re blue collar and often got into the trades by pure necessity to support their families, he added. Then they saw an opportunity to start their own businesses and eventually built them up.

But not every plumbing or HVAC business is a good fit for Redwood. Lewis said he’s looking for partners who have more to offer and aren’t just wanting a quick buyout with no involvement afterward.

If the first thing an owner asks is how much their business is worth, that’s not for Redwood. Rather, Lewis wants the first question to be “how is this good for my people?” Once he sees that the company’s culture is right, then hell ask about financials in a follow-up conversation.

There’s no typical partner. They can be in their 60s, or a husband-and-wife team, or a father-and-son team. Instead of fitting a certain mold, Lewis wants to hear a potential partner’s story.

“I want to get to know their personal journey in life, you know, were they given this business by their parents and they’re just there to collect a paycheck?” he explained. “Or were they one of the guys that grew up in the back of a truck and started from scratch and built something special?”

To be sure, private equity isn’t new to the trade sector, and Lewis counts 64 other firms he is competing with.

But he believes Redwood has a unique approach where he zigs while others zag, translating to explosive growth.

“When we started this business four years ago, I was afraid that if everyone’s doing it this way and we’re over here doing it that way, maybe I’m just a complete idiot and this thing is going to fall flat on its face,” he recalled.

“Fast forward four years: We’re one of the fastest growing investors in the industry. We’ve gone from zero million of revenue to $400 million of revenue in four years. The business doubles every year, so I think we’re doing something right.”