At Mar-a-Lago, Donald Trump’s waterfront winter retreat, an end-of-term air hangs over the expansive verandas and perfectly manicured lawns. In barely a month’s time, following the traditional season-closing Easter Sunday brunch gala, the private members’ club will be scrubbed and shuttered for the summer, its wealthy clientele dispersing to residences in the Hamptons or boarding their mega-yachts to cruise the Mediterranean.

With the winding down of the annual Palm Beach social circuit comes the end of another season of controversy, scandal and ethics concerns that swirl around the exclusive resort, which drips with gold-leafed opulence and where a $200,000 “initiation fee” appears to cover the privilege of bending the president’s ear.

This year’s cast of notable characters includes the Chinese former owner of a massage parlour snared in a high-profile prostitution sting, a Russian investor wanted in his home country for tax fraud and a cosmetic dentist who influenced Trump’s thinking on veterans’ care by writing policy advice on a cocktail napkin.

Add to the mix last summer’s confirmation as ambassador to the Dominican Republic of Trump’s longtime friend and former insurance agent Robin Bernstein, a Mar-a-Lago founding member, and renewed concerns by ethics experts over the ease of access to and influence over Trump when he visits his resort are easy to understand.

The Mar-a-Lago club has turned into a pay-for-access to the president club Robert Weissman, Public Citizen

“The Mar-a-Lago club has turned into a pay-for-access to the president club, with a president with almost no knowledge of governmental policy,” said Robert Weissman, president of Public Citizen, a Washington-based pro-transparency group that has criticised Trump for continuing to profit from his business operations while in office.

“If you can whisper in his ear and tell him anything, he may well think it’s sensible and he may well act upon it.

“There’s no reason to believe people he’s picking out of the field at Mar-a-Lago are qualified to serve as ambassadors for the US or in any governmental position but they’re paying, they have access, they’re buddying up and they get to use serious positions as casual rewards.”

Of equal concern, Weissman said, is that the most powerful man in the world could be so easily manipulated by those whose credentials as policy advisers seems based solely on wealth.

“Long ago presidents were very accessible and the White House was open, but even then the access wasn’t based on your ability to pay a $200,000 cover fee,” he said. “There’s absolutely no precedent for this kind of paid-for access, and there’s no precedent for a president who is so responsive to random bits of information because he has no views of his own and no background knowledge of his own.

Donald and Melania Trump at Thanksgiving dinner last year. Photograph: Susan Walsh/AP

“If there had been a comparable situation with Barack Obama, whispering in his ear might have been important but it wouldn’t have shaped his world view or had him go off on some new path because he would have known what you were talking about. He had his own views already, and that’s just not the case with Trump.”

The Trump administration appears immune to a catalogue of embarrassing headlines, among them the story of Li “Cindy” Yang, 45, the Chinese American founder of a day spa where Trump’s friend Robert Kraft, the owner of the Super Bowl champion New England Patriots, was arrested and charged with soliciting prostitution, which he denies, in February.

Yang, a Republican fundraiser and donor who was photographed with Trump in a Super Bowl party selfie at his West Palm Beach golf club, and also at Mar-a-Lago with Florida’s Republican governor, Ron DeSantis, sold the massage parlour where Kraft was arrested several years previously. She still owned others.

But follow-up coverage by the Miami Herald and Mother Jones said Yang owned a consulting business that promised Chinese investors access to Trump at Mar-a-Lago and had arranged for a group to attend a Trump fundraiser in New York in 2017, testing strict rules prohibiting foreign involvement in the US political process.

That forced a denial from the White House that Trump knew Yang, and a fierce denouncement from her lawyers of any wrongdoing.

“She is being accused of human trafficking, providing favours to Chinese politicians and businesses by selling access to the president,” attorney Michelle Merson told NBC News. “She denies everything.”

The Yang saga was followed by another eye-opening scandal this week when the Herald exposed the presence at a Mar-a-Lago charity event last year of Sergey Danilochkin, a Russian real estate investor accused in his home country of a $170m tax fraud. There is no suggestion he met Trump, but the Herald reported he was there as part of a $600-a-head event hosted by Elizabeth Trump Grau, the president’s sister.

Neither the White House nor the Trump Organization answered the newspaper’s questions about how Danilochkin gained access.

‘When he’s there, it’s a circus’

Some of the more extraordinary and questionable moments at Mar-a-Lago have their roots closer to home, and involve club members. Palm Beach handbag designer Lana Marks, for example, is Trump’s pick for US ambassador to South Africa.

Donald Trump and Chinese president Xi Jinping at Mar-a-Lago on 7 April 2017. Photograph: Jim Watson/AFP/Getty Images

More bizarrely, Trump’s dentist, Albert Hazzouri, scribbled a note on a Mar-a-Lago napkin, inexplicably addressed “Dear King” and proposing ways to eliminate what he saw as waste in federal spending on dental care for former military personnel. According to ProPublica, Trump endorsed the napkin with a “the president has seen” stamp and ordered it forwarded to David Shulkin, then secretary of veterans’ affairs.

Hazzouri told ProPublica: “I’m not really involved in politics, I’m just a small-time dentist.” But Trump placed enough value on his thoughts to send them to the agency responsible for the health of 9 million ex-servicemen and women.

No policy should be done this way. He thinks it’s cool Jose Lambiet

“When he’s there, it’s a circus,” said Palm Beach society writer Jose Lambiet, who has chronicled Trump’s tenure at Mar-a-Lago since he bought the 126-room, 1920s-built mansion from the estate of the late cereal heiress Marjorie Merriweather Post in 1985.

“It’s not just the ethics of this, but the visuals are terrible. No policy should be done this way. He thinks it’s cool, that he was elected for this stuff, but I don’t think he was. The ethics of people having access to him through Mar-a-Lago should be investigated because it allows rich people to have access to him in a way that regular people don’t.”

Lambiet said Trump has always enjoyed the theatre of playing host.

“He comes out in the early evening, he walks around and he shakes hands with everybody. He always thought that even when he was just a TV celebrity or businessman, the reason for people to pay that kind of money, and back then it was $100,000 to join, was for him. He didn’t think they came for the beautiful scenery or the food.

“Now he’s president there’s more hangers-on. The characters have changed in the sense that Palm Beach society has been replaced with people with a lot of money but not necessarily a lot of class.”