Danny Burstein and Rebecca Luker in Morningside Heights
When they began looking for an apartment to buy just before their wedding nearly 15 years ago, the Broadway performers Danny Burstein and Rebecca Luker could not have been more clear with their broker: They weren't interested in seeing anything past 96th Street, and that was that. What with both of them tethered to the theater district, they wanted a short, easy commute to 42nd Street. So nothing doing north of 96th.…