Goldman Sachs’ acquisition of United Capital for $750 million in cash will give the storied New York investment bank an opportunity to reach more high net worth clients, namely those with $1 million to $15 million in assets.

Currently, Goldman Sachs works with the wealthiest of individuals, or those with at least $25 million in net worth, and its private wealth management group manages $427 billion.

(More: What does a Goldman-owned United Capital mean for advisers?)​

With its acquisition of United Capital, announced Thursday morning but rumored in the financial advice industry for weeks, Goldman Sachs will bring wealth management to “a broader array of people than the firm currently works with,” said Joe Duran, founder and CEO of United Capital.

The acquisition is scheduled to close in the third quarter.

United Capital is a “drop in the bucket” when compared to Goldman Sachs’ private wealth group, Mr. Duran said. But he added that Goldman expects the acquisition to be the fastest growing part of the wealth management segment. “We want to double the business in relatively short order,” he said.

“This is a huge growth opportunity for them and us,” Mr. Duran said. “We want to be the dominant player in financial advice business.”

“I’m unbelievably thrilled to be on a bigger stage,” Mr. Duran said.

United Capital has more than 220 advisers and $25 billion in assets under management. It also offers advisers a digital platform, FinLife CX.

In an interview, Mr. Duran said he could not comment whether he was now a partner at Goldman Sachs but characterized his position at being at the “most senior levels” of the bank. He also said that owned more than 10% but less than 20% of United Capital, which he launched 14 years ago, putting his payout in the deal in the neighborhood of $75 million to $150 million.

Wall Street’s biggest players have been slowly but surely expanding their reach into larger parts of the wealth management and financial advice markets.

Morgan Stanley in February said it agreed to buy Solium Capital, an employee stock plan manager, for $900 million. And in November, BlackRock said it planned to buy a 4.9% equity stake in Envestnet.

“This deal is very interesting for Goldman” said Shirl Penney, president and CEO of Dynasty Financial Partners, in an email. “On the surface it helps them execute their stated game plan to widen the firm’s footprint in wealth management. It also gets them in the RIA space, which has been the hottest and fastest-growing segment of wealth management industry.”

Goldman CEO David M. Solomon cited the bank’s wealth management offerings, which have $500 billion of AUM, and its goal of serving clients “across the wealth spectrum.”

“United Capital will help accelerate this strategy by broadening our reach, allowing more clients to access the intellectual capital and investment capabilities of Goldman Sachs,” Mr. Solomon said in a press release announcing the deal.

In its press release announcing the deal, Goldman Sachs included a diagram of its line of wealth management businesses.

United Capital sits below — but is linked to — Goldman’s three current business: Marcus, its digital consumer finance business with $46 billion in deposits; Ayco, its retirement plan and wealth management platform that works with more than 400 companies and has $55 billion in assets; and its private wealth management group.

United Capital will be connected to Marcus to enhance its digital capabilities, and also provide “high-quality” referrals to Goldman’s private wealth group, according to the release.

United Capital will be expanding to cities where Goldman and Ayco have clients that need greater support, Mr. Duran said. That could mean adding more advisers in the future, he said.