Jeffrey Horowitz is selling his oceanfront Hamptons estate for $89 million, but the purchase comes with a catch.
Whoever buys 21 Fairfield Pond Lane in Sagaponack will also become owner of the adjacent plot — 407 Fairfield Pond. The mansion is priced at $75 million, and the land is $14 million, but the owners want to sell both, said listing agent Kieran Brew of Serhant.
"This is very unusual for any property in the Hamptons, let alone an oceanfront compound," Brew told Homes.com.

The mansion is 9,000 square feet and features eight bedrooms and 10 bathrooms. Its interior has a fireplace, a finished basement, and a three-car attached garage. Outside, there's an in-ground pool, spa, wildflower garden and pond.
The home — built in 1998 — rests on a 2.1-acre lot and out back is a 200-foot-wide walking path to the Atlantic Ocean. The back of the property is protected by a rock revetment designed to keep ocean water from reaching the home's foundation. Brew noted that the home is in a flood zone, meaning the new owner must purchase flood insurance.
Horowitz, a pharmacist by trade who founded the company in New York City in 1977, has a private golf course on the 407 Fairfield plot, which is directly west of the mansion. The space could be converted into a tennis court, a pickleball court or even another home that could be sold or occupied by family, Brew said. New owners would need to hire a landscape architect to revegetate the plot and get it ready for a different structure, Brew said.
"It's a very expensive process with a lot of experts," he added. "It's not a DIY project."

Horowitz and his family members are reluctantly selling the home and land despite knowing how unique both properties are, Brew said.
"Like most people, this has been their family home for decades," he added. "It's bittersweet for them, but they're selling for personal reasons even though they love the place."
Sagaponack is known for having some of the most expensive homes in the Hamptons. English colonists settled on land that is present-day Sagaponack, but the village wasn't incorporated until September 2005. Sagaponack is also home to one of the few remaining one-room schoolhouses in New York — the Sagaponack School.
Median home sales prices in Sagaponack are around $5.4 million, according to New York brokerage Douglas Elliman.

Wanting to sell both properties has limited the number of potential buyers interested in the home, but those who have viewed it were impressed by the primary bedroom, Brew said.
"It's got a gorgeous terrace overlooking the gardens, the pool, the dunes and the ocean," he said. "But almost every room of the house has a view of something spectacular. Even if you're in one room that doesn't face the ocean, you're facing the pond and golf course and that's where the sun sets in the summer, so it's pretty special, too."