This home — known as “1009″ within the family for its address on Fifth Avenue — was a grand residence, but hardly a happy one.

Ben Duke moved in in 1901 but his frail health prevented his enjoying it. He and his wife Sarah discovered they preferred Durham anyhow. He let his brother James B. use it for his first marriage, a union that ended effectively during the honeymoon and legally less than a year later. Ben gave it to his daughter Mary — pushing 30 — when she married a teenager from Philadelphia — Anthony Biddle.

This marriage also ended in disaster — the split causing Mary Duke Biddle to spin into a deep depression that would disable her ability to function, a condition so bad that Ben’s widow Sarah was impelled to go to the mansion to rescue Mary Duke Biddle II, now Mrs. Semans, and bring her grandchild back to Durham.

The house then stood empty for decades, well maintained, even spruced up as a project for Mrs. Seman’s son, used very rarely except for events such as the family gathering under matching crystal chandeliers in a second floor parlor to mourn the passing of James B.’s only child Doris Duke.

Location, location, location. The first three rules of real estate actually subtracted from the value of this home. Rather than looking into Central Park, the mansion faces hard into the giant stone facade of the Metropolitan Museum of Art. Even from the sixth story roof, the view is disrupted by the museum, which is a lot better than what’s at the front door nowadays: a hot dog cart surrounded by tourists.

The Dukes are very possessive of their real estate. Witness James B.’s getaway, Duke Farms in NJ, a 700 foot long house closed to the public and 4.21 square miles to be preserved forever as a public park. And two homes that welcome visitors: Rough Point, his ocean mansion in Newport, Rhode Island, and Doris’ Shangri La at Diamond Head in Hawaii. An appraiser looking at some of her Muslim art there told Doris that he had seen $1 billion, and she said to stop.

The first sale of 1009 had to jar the family: the purchaser had money but hardly a pedigree. Starting as an Russian immigrant, Tamir Sapir, original name Temur Sepiashvili, cab driver, cab fleet owner, oil and fertilizer trader with heavy, questionable ties to the Soviet government, said he was going to turn it into a showpiece for his collections. Mrs. Semans said some kind, proud cultural things.

Whoops. Decorative animal hides, stuffed heads and ivory carvings are illegal to have in the U.S., an endangered species law lost on Sapir until charges were brought. Add in the sputtering of his own fortune (down to $1.4 billion at least report), he installed no museum but flipped 1009 for a ten percent profit after owning the mansion for four years, enough time to install two grotesque bigger than life statues under the front door canopy.

The buyer is another billionaire: Carlos Slim (he’s anything but) Helu, the wealthiest man in the world (Forbes, $53.3 billion) because Bill and Melinda Gates have been giving away so much. He’s Mexico’s telecommunications czar and New York Times investor/savior.

The white shoe New York real estate broker Brown Harris Stevens had an exclusive listing on 1009 — but Sapir and Slim waited and did a private deal the day after the listing expired, s sale that’s pissed the brokers who got no commission. Ah those wealthy people.