must building provide ramp?

I would suggest you consult the city for advice:
http://www.nyc.gov/html/mopd/html/home/home.shtml

if there is an available way for you to enter without steps, that's the way you enter. you want to be special, you will have to pay for special.

http://www.nyc.gov/html/cchr/html/coverage/housing.shtml
http://www.nyc.gov/html/mancb12/downloads/pdf/disability_housing_rights_and_building_codes_of_new_york.pdf
http://www.brickunderground.com/files/Riverbay%20vs%20NYS.pdf

Landlord must provide access at its expense
Access must be to the main entrance, not the service or basement; separate but equal not adequate.

Have fun.

"you want to be special"

Hmmm, I could be wrong, but i kinda doubt the OP "wants" to be in that wheelchair. OP?

mucuk is correct. There was a recent case where Co-op City tried to get away with providing an around-the-corner means of access. No go. If there's no room for a ramp, the landlord can install one of those lifts.

Welcome to America mucuk

Unless you have the (mis)rtune to live in a landmark district which are allowed, nay mandated to discriminate against the disabled. My mother's building in the West Village, hardly of particularly historical merit, renovated the entry area a few years before she passed away and I was was delighted thinking there would now be a ramp that would allow her to use a desperately needed walker. No dice, the Landmarks Commission dictated that the entry look like it did previously--exact duplication and the disabled be damned.

no, ab_11218v, i don't want to "be special." what i want is to be like all the other tenants in the building, who have a canopied entrance, a doorman, a beautiful tiled lobby, and quick access to the elevator. instead, i must stop by the front of the building to ask the doorman to open the back gate, then travel around the corner and halfway down the block to enter a long alleyway that leads to the basement entrance, and then go down a long depressing hallway to the elevator.