Remember how in college, you'd fill in your 1st, 2nd, 3rd, etc. housing options and get a match? Do that with groups of friends who are all graduating college at the same time and moving to NYC. Landlords would love you, as you'd rent out entire floors/buildings all at the same time.

Then build an ongoing matching service to fill the spots of individuals who move out.

NYC real estate is physically shitty, so you can add value by focusing on the social aspect of living.