In most cases the simple answer is yes, you do have to comply with the accessibility requirements of the NYC Building Code. Exception 5 of Section 28-101.4.3 of The administrative code requires all building undergoing alterations to comply with Chapter 11 of the building code for accessibility.
Section 1101.3 gives special provisions for prior code buildings which do provide some relief when the entire building is not being altered. However, any and all spaces that are being modified must comply to the extent that they are altered.
In the case of a Condo renovation all spaces in the condo, up to and including the entrance door, that are being altered must provide features complaint with the requirements for a “Type B + NYC” dwelling unit.
Chapter 11 does provide additional exception and relief for certain building elements such as bathrooms, but as a whole the unit is not exempt form accessibility requirements.
Select areas in Brooklyn may now be permitted to create lawful cellar apartments.