Unbeknownst to most fans outside of New York City, Robert De Niro is a landlord. He owns a still-trendy restaurant, the TriBeCa Grill, which opened in the very early ’90s and still caters to a starry crowd. Now the Oscar winner (“Raging Bull”) could very well be adding another hot property to his Manhattan real estate portfolio: a boutique hotel. The New York Observer newspaper reports that the star, 57, and hotelier Richard Born are looking into opening a chic little inn right next door to the Grill. (De Niro already owns the TriBeCa Film Center next to that, where several film companies have their executive offices and post-production facilities. In addition, De Niro lives in a verdant garden penthouse in the neighborhood.) “He is very easygoing and pleasant,” De Niro’s prospective business partner told the Observer, “and very easy to deal with.” And he certainly has the dough to play the real estate game. For the recent “Meet the Parents,” De Niro’s salary was reported to be $13.5 million.