The Mystery Company With One Foot in the Premier League

777 Partners had been scooping up big-name soccer teams for two years when it bid for Everton. Doubts about its finances could kill the deal.

The acquisitions came so quickly that it was hard to keep up. An agreement to buy the oldest soccer team in Italy. An investment in one of the most popular teams in Brazil. Stakes in well-known clubs in Belgium and France, Germany and Australia.

Each new deal was trumpeted by the Miami-based investment company, 777 Partners, that was hurriedly snapping them up.

Then, in September, the investment group revealed its biggest deal yet: an agreement to acquire a controlling stake in Everton F.C., a founding member of the Premier League and one of the oldest soccer clubs in England.

Suddenly, everyone in soccer had heard of 777 Partners. Beyond its name, though, little was known about the company. It said it had $10 billion in assets, but was so closely held that verifying that claim was difficult. Lawsuits against the firm raised concerns for potential partners. A string of unpaid bills, some as recent as this month, raised more.

Now, in bidding for a place in the Premier League, 777 Partners faces something it had previously avoided: a forensic review of its holdings, its finances and its brash American co-owner, Josh Wander, who in one recent interview said he was “more serious about investing” in soccer than anyone in history.

His company’s bid for control of Everton, an acquisition that would eventually require hundreds of millions of dollars in assumed debt and other obligations, is by no means a sure thing. The Premier League, England’s Football Association and an independent British government regulator, the Financial Conduct Authority, all must approve the proposed deal, a process that is likely to take months.

What they discover could have implications not only for the future of Everton, a fallen, money-losing giant, but also for rest of the financially troubled teams in the 777 network.

The stakes are just as high for the Premier League, which is trying to prove it can oversee its clubs’ finances amid talk of government regulation, and for an interconnected global soccer economy reliant on the simple premise that teams can and will pay their bills.

None of the soccer or public agencies currently assessing 777 Partners would discuss their review or a timetable for its conclusion.

Mr. Wander, the co-founder and public face of the company, declined multiple requests to be interviewed for this article, though he published a long letter to fans on Everton’s website on Saturday in which he acknowledged fans had been discomfited by media reports about the company’s businesses. But those reports, he said, were “misleading.”

“The truth is far more boring than the fiction,” he wrote.

“We are not asset strippers nor speculative investors. We build and hold businesses, and intend to hold the football clubs in our portfolio for a long term,” a spokesman for 777 wrote in an emailed statement. In the letter to fans, Mr. Wander wrote that he would share “player recruitment, data analytics and commercial development resources,” with the other teams in the group.

More than a dozen current or former employees, club officials and others who have done business with 777, however, revealed new details and questions about the sources of its financing. The people asked not to be named because of relationships with the company.

In interviews, they also shared details about unmet obligations and unpaid bills, and wondered if the company has the resources to manage a global network of clubs carrying hundreds of millions of dollars in debts and obligations.