Private islands in New York can cost up to $3 million, according to Private Islands Online, an online marketplace listing private island sales.
But Columbia Island in New Rochelle, New York, about 30 minutes from Manhattan, is on the market for $13 million.
For 11 years, the current 85-year-old owner Al Sutton, a real estate developer and former physician, spent $8 million to build a sustainable home on the island, according to Robb Report, with the intention to potentially live in it.
"I was more ambitious when I purchased it," Sutton tells CNBC Make It, "and now in my 80s, it's not as practical," so he is selling it.
The home is built on bedrock, which is the same geologic feature that supports Manhattan skyscrapers that provides stability, according to a representative from Sotheby's International Realty, the agency handling the listing, and is surrounded by a 5-foot seawall and landscape decking for storm and flood protection.
The home is self sufficient. It has solar panels for electricity and diesel generator back-ups; a reverse osmosis water filtration and desalination system for clean water; in-floor radiant heat with boilers and hot water-heat exchanger; and a sewage system.
Another reason for the high price is the location, according to Sutton. The island is about 30 minutes "fast boat" to East 34th Street heliport, according to Bloomberg.
The 5,600-square-foot home on Columbia Island has four bedrooms and two bathrooms, as well as an open kitchen and dining area overlooking Long Island Sound, according to the listing.
There is a great room "with views from every angle."
The master bedroom has large windows for views, as pictured in the rendering below. The master bathroom has a large rain shower, as seen in the rendering.
The home has a private dock. The island is only accessible by boat.
The sale includes neighboring Pea Island, which is 2 nautical miles from Columbia Island.
Both islands were previously owned by the Huguenot Yacht Club and Pea Island was often used as a "party island," according to Sutton, who declined to further comment on what activities took place.
"Huguenot Yacht Club used it for their club members prior to selling it to me." Huguenot Yacht Club was founded in 1894, according to the website, and offers "yachting events, races and much more."
"They had snacks, cabanas, boating activities and mothers would take their children out for the day," Sutton says a Huguenot Yacht Club member revealed to him, "also partying, with drinking, though not wild. It was largely wholesome."
The islands are less than a 10-minute boat ride from mainland New Rochelle, which is part of Westchester County. The median household income of New Rochelle was $77,320 in 2013-2017, according to the most recent US Census data from July 2018.
Columbia Island is the only private island for sale within 50 miles of Manhattan, according to Sotheby's.
Columbia Island was owned by CBS in the 1940s to 1960s, according to Sotheby's. It was later owned by Peter Lind Hayes and Mary Healy, former TV and radio entertainers, then owned by the College of New Rochelle. Sutton bought the island from the college in 2007 for $1 million.
Additionally, Sutton spent "approximately $500,000" for Pea Island, which is "undeveloped" and "approximately 5 acres," Sutton tells CNBC Make It.
You can see Pea Island from the home.
"The space is an ideal retreat for a private buyer as well as groups," says Sutton. "Sports stars would certainly have the means and desire to have such a property."
Ever since Sutton bought the island and worked on building the home, nobody has actually lived in it because "construction was always in progress," Sutton says. "Someone can live there now because the majority of the work is done, specifically the infrastructure," he says. "And it is a serene and naturally beautiful spot, and quite the unique property."
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