Yes, you can make it on the stipend if you take the campus housing or go to less than an ideal location. I thought most starting nyu students live near by, but I must be wrong. You're right that older students commute and you can find apt for under 1000 in the boroughs--and a decent one if you share. The prob with boroughs is that on the weekends, several train lines get rerouted due to construction, and depending on where you live, you either have to take the bus or taxi when you get out of the library at 2am. More time mgmt and planning required.
All depends on the definition of 'decent'. I agree that there isn't much time to spend $ while in grad school. But $3000 summer stipend... even subsidized housing is about 1K a month, so how do you make it if you don't take RA or something?