William Ganz knew it was a big investment, but with “The Donald” involved, he felt certain he would strike gold.

It was May 23, 2007, and the 28-year-old Baltimore-based entrepreneur was preparing to invest his life savings in Trump Farallon Estates at Cap Cana, a luxury development being planned by local developers in the Dominican Republic and championed by his famously gilded business idol, Donald J. Trump.

Ganz had read every one of the real estate mogul’s books and even auditioned for a spot on “The Apprentice,” so when Trump called the project a “fantastic opportunity,” Ganz believed him. The Trump brand, he said, brought the project “instant credibility.”

The same day buildable lots in the cliff-top resort went on sale, Ganz and dozens of other buyers bought out 95 percent of the development, snapping up more than $350 million in property. As Trump described it in videos and in person, there would be a condominium-hotel, a beach club, private villas, and a world class golf course.

But the development never took root, a failure some blamed on the 2008 financial crash. After investing years of work -- his savings gone and his spirit broken -- Ganz left his island dream behind.

“The air was out of the balloon,” he said.

For Ganz and the scores of others who lost millions on the Trump Farallon development, that should have been the end of the story. But shortly after Trump took the White House, Trump’s son was back in Cap Cana. The developer issued a surprise announcement in February 2017, releasing a smiling photo of Eric Trump on the bluffs of the Dominican coast, emerald waters at his back.

“This relationship remains incredibly strong, especially with Eric, who has led the project since its inception,” the developer announced.

News of what the Trump Organization was describing as a “new phase” of Trump Farallon never reached the project’s original buyers, according to those interviewed by ABC News.

Using records made public in court documents, ABC News located 48 of the original property owners from the Trump-branded Cap Cana resort. A quarter of those agreed to talk about their experience, though most spoke only on the condition they not be identified. Many who did speak said they still felt stung by the failed investment. Like Mariano Gonzalez, a Puerto Rican doctor who had pooled a big chunk of his life savings along with two friends to invest $3 million in land atop the scenic cliffs overlooking the turquoise Caribbean waters.

“We were betrayed,” Gonzalez told ABC News. “Nothing was done and everything was lost. My main message is, ‘Give me back my money.’”

One reason Gonzalez and others were so surprised to hear of Eric Trump’s return to Cap Cana was because it seemed like it had all ended so badly.

In a blistering lawsuit filed in 2012, the Trump Organization accused the developer of having “grossly underreported” the project’s sales figures to avoid having to pay the Trump company its share of the proceeds. “This was textbook fraud on a wide scale, involving millions of dollars,” the Trump lawsuit alleged.

The developer of the Cap Cana resort, Ricardo Hazoury, never mounted a public response, beyond arguing the suit belonged in the Dominican Republic, not the U.S. The case settled a year later in secret. The Hazoury family declined through a New York attorney to be interviewed or answer written questions for this story. The Trump Organization also did not respond to requests for comment, other than to say that the project’s revival in 2017 was not unexpected to them.

“The project has multiple components or phases to be built over time,” said Alan Garten, a lawyer for the Trump Organization. “That’s how it was structured from day one.”

Unlike many of the original buyers – many of whom saw their land lost to foreclosure – the Trumps made money. According to the court records, the Trump Organization received some $12 million in licensing fees. They resolved their legal claim in an undisclosed settlement, the records show.

Concerns about potential conflicts

More than a year after Eric Trump’s return to Cap Cana, the plans for a new Trump-branded Dominican development have remained shrouded in secrecy. But the potential revival has raised a host of thorny questions, not only for the dozens of original buyers who lost money in the planned Caribbean resort, but for both ethics groups and the president’s congressional critics.

The Dominican project, they argued, offers a fresh example of the issues raised in U.S. District Court on Thursday. Lawyers representing nearly 200 Democrats in Congress argued in a lawsuit that President Trump is violating the Constitution by accepting potentially profitable favors and business opportunities abroad.

“The problem is clear, and the implications for U.S. national security are serious,” said Sen. Benjamin Cardin, a Democrat from Maryland, who is a plaintiff in the suit and a leading member of the Foreign Relations Committee. “In country after country, it is a major problem when the Trump Organization conducts business because that business financially benefits President Trump, just like here in the Dominican Republic.”

For Cardin and other members of the Senate Foreign Relations Committee, the chief concern has stemmed from allegations of favorable foreign treatment to Trump businesses. Trump has pledged that his family’s company would avoid any new foreign enterprise, but without adhering to that pledge, Cardin told ABC News, “the American people are left questioning whether the President’s decisions abroad are made only in the U.S. national security interest or with regard to his business interests.”

The Trump administration and the President’s family company have repeatedly rejected any suggestion that a conflict could emerge in countries where the Trumps are in business. During a Foreign Relations Committee hearing, Secretary of State Mike Pompeo responded to a question about the potential for U.S. foreign policy to conflict with Trump ventures abroad “bizarre.”

“I've been incredibly involved in this administration's foreign policy now for some sixteen months and I have seen literally no evidence of what you are scurrilously suggesting,” Pompeo said.

Watchdogs in both the Dominican Republic, and the United States however, aren’t so sure.

Bernardo Vega, a leading Dominican news columnist who once served as the country’s ambassador to the U.S., told ABC News he wants to know if the developers who are working with the Trump Organization are receiving special treatment as they have sought to acquire permission to build 20-story hotel towers in a part of the island where building heights are severely restricted. Vega wrote a newspaper column alleging special treatment, but the tourism officials denied that to ABC News.

Vega has continued, though to voice his concerns to reporters, telling the U.S. publication Fast Company in February: “Here in the palace, the president’s thoughts are that this U.S. president is angry and we better not get in his way. We don’t want to cross him.”

The former U.S. ambassador to the Dominican Republic, Wally Brewster, told ABC News he wants to know if any of the president’s broad range of powers have become tools of leverage in the company’s dealings with the powerful Dominican family that is developing Cap Cana. Brewster, who was an Obama appointee, noted that Dominican business executives treasure their visas. Even if the topic is never mentioned, he said, just the fear they could lose their U.S. travel visas could give the Trump Organization an upper hand in any negotiation.

Brewster said he does not know if visas were ever invoked in discussions over the Trump development. But he said “the threat of potentially having your visa pulled can be just as powerful as having it pulled,” he said.

Brewster also questioned whether the U.S. government is still aggressively pursuing a slow-moving legal case it brought against the project’s developer for more than $12 million in U.S. loan guarantees issued by the Export-Import Bank of the United States but never repaid. The loans, bank officials told ABC News, were meant to help the Cap Cana developer to import U.S. products. But Dominican court records show efforts to recover the U.S. taxpayer funds have stalled. There has been no action on the case since August 2016.

Eryn Schornick, a lawyer with the watchdog group Global Witness told ABC News these are concerns inherent with having a U.S. President whose family is doing extensive business overseas.

“The primary concern I see with the potential of Mr. Trump’s family returning to the Dominican Republic is abuse of power,” said Schornick, who has done legal work in the Dominican. “The fact is, the Dominican Republic is a very small country. They’re in a place where doing business with [the family of] the President of the United States could influence the way in which any negotiations in foreign policy may happen.”

In Cap Cana, snakes and high grass

Fausto Peyrani, an Italian businessman, gave ABC News a tour of the lot he purchased at the lavish sales event a decade ago.

He drove slowly up the road to the 68 cliff-top lots that had sold in 2007 for between $3 million and $12 million, past the helipads where sales teams offered buyers helicopter tours of the building site, and the tropical restaurant with koi ponds where Trump and his children, Eric and Ivanka, greeted buyers amidst an endless spread of gourmet food and champagne. The glass windows and doors were shattered, and overgrowth had begun swallowing the walls and over-running the Koi ponds. A snake could be seen slithering behind the bar.

On his property, a steel tower once erected to provide a view-scape of the bluffs below had rusted and started to buckle.

“Ten years ago, I like many others were absolutely certain that this place would develop rapidly,” he said.

Now, he does not hold hope for living long enough to see the mansion he imagined building on the property. “I think my great, great, great, grand grandchildren, in 30 years will say, ‘Oh we had a very smart great, great, great grandfather.’ But, all those in between, are not going to see anything.”

Gonzalez told ABC News that he still remembers being greeted at the sales event by Eric and Ivanka Trump. And he still has the letter he received, a copy of which can be read below, signed by the man who one day would be the American president.

“You can rest assured that Cap Cana will be up to the gold standard the Trump name signifies worldwide,” Trump wrote in 2008. “I have no doubt that Trump at Cap Cana will be no exception in achieving the usual success that we have come accustomed with [sic] all of our products around the world.”

Now, he grimaces when he writes the monthly $129 maintenance checks to insure he is in good standing with the developer. He stopped visiting years ago and no longer expects to see signs of activity.

“The grass was growing over the roads. There was a big fountain as you came in, [but] the fountain broke down, it was not functioning,” he said. “It [had] deteriorated. You could see that there was nothing going on.”

Ganz, now a Baltimore real estate agent, also said he has not heard from anyone about the “new phase” of the development that gave him his first tough lesson in the harscrabble world of real estate. He says his life has moved on since he says he ran out of funds to maintain the property and his bank took ownership of the land.

The one-time Trump true believer has chosen to harbor no grudges against the Trump Organization for what went wrong. “For people to look back frustrated, or say things weren’t delivered, or it was false advertising, or improper marketing practices, I don’t really take that perspective.” And he said he still holds out a glimmer of hope for a return.

“I think there’s a lot of frustration with the overall body of investors that purchased in Farallon, but I take that in stride,” Ganz said. “To me the best thing that could happen would be to help me finish what I started down there. And, hey, the ship has righted, train's back on the track, and the American dream continues in the Dominican Republic.”

If you have information about this or a similar development, please contact Matthew Mosk (matthew.mosk@abc.com).

ABC News' Halley Freger contributed to this report.