Howard Hughes Holdings Inc.’s stock rose Monday as billionaire Bill Ackman reached a final agreement to acquire a controlling interest in the real-estate-development company that he plans to turn into a modern Berkshire Hathaway.

Ackman is assuming effective control of Howard Hughes, a listed real estate development company he already partially owns, with a further $900mn investment in the Texas-based group. Under the agreement,

The deal involves Pershing Square buying 9 million newly issued shares of Howard Hughes for a total cost of $900 million. The purchase price is 48% above where the stock closed Friday, and puts Pershing's stake in the company at 46.

Howard Hughes Holdings said Bill Ackman’s Pershing Square Capital Management will invest $900 million in the company, boosting its stake further and bringing Ackman back into the fold.

Pershing Square agreed to invest $900 million in the company known for master planned communities, Bloomberg reported. Ackman’s firm will acquire 9 million newly issued shares of Howard Hughes for $100 apiece, a 48 percent premium on the stock’s closing price ahead of the weekend.