You and I are living a similar life, just flipped. I was born and raised in NYC, went to LSU for undergrad, and have recently been accepted to a handful of MSW programs, one being an ivy. My hope and dream was to go to Tulane for my MSW and thought the ivy was a pipe dream. Until I got in, that is. So now I'm stuck between Tulane and Penn. My father claims that choosing Tulane would be the biggest mistake and I would regret it for the rest of my life. Anyway.. enough about me.
How far along are you in your MSW program? If you're about to graduate and will be able to get a job in NYC, I can't imagine why you'd be homeless. Rent is out of this world, but if you have a roommate, it's managable. My brother (who goes to Cooper Union) is paying somewhere in the neighborhood of $900 for his shoebox, which is ridiculously cheap for the neighborhood, but again, it's a shoebox.
What is your career goal? Do you plan to use your MSW? Is the masters in creative writing just an excuse to go to NYU? If you're dying to go to NYU, why not just apply to their social work program and call it a day, rather than spending however many more thousands upon thousands of dollars to get a second masters? I get the unsupportive family thing, since my parents didn't talk to me for 3 months when I told them I was going to LSU. But they got over it and your parents will, too. If you want to go (and it'll make financial sense), then go.