In New York, where real estate often runs in the family, Richard Maidman, 78, fits right in. He is chairman of Townhouse Management Company, which grew out of a dress company founded in 1933 by his father, William, and he works alongside his son Mitchel, who serves as the company’s president. But the Maidmans may be most closely associated with another real estate clan, the Dursts. For decades, the two families haggled over 113 West 42nd Street, a narrow high-rise owned by the Maidmans that the Dursts needed to raze to make way for the Bank of America tower. Both sides finally struck a deal, and the Dursts picked up the building for a reported $13 million. Today, Townhouse, which owns or manages 60 rentals, co-ops and condos in Manhattan and the Bronx, is leasing 35-39 East 63rd Street, a new luxury rental where one bedroom rents average $10,000. Maidman’s office, meanwhile, is decidedly more modest, shoehorned into the basement of a Midtown high-rise where the rent is $27 a foot.