You could also check out any Youth Hostels in the area. I’m not sure how many there would be in Manhattan and they are not free, but about the lowest rates you will find. They are primarily for travelers, but I came across a reference to a place that is specifically for college students. I can’t remember the name, but will check my bookmarks to see if I can find it.
You didn’t mention how long a period of time you want this for, but there is another possibility if you are willing to barter for it with a minimum amount of work. There are elderly folks whose families are searching for someone to primarily be there at night since they don’t want them totally left alone. But, obviously this would not work for you if you are the partying type.
If this appeals to you, you could place an ad in Craigslist. You can also contact various caregiving agencies. Nighttime positions are usually the hardest ones to fill. Occasionally someone looking for a nighttime caregiver/companion may place an ad in the medical/health section or even under the rooms category in housing.
This is a link to something sort of like what I described, but it’s for a young person with an injured leg.
http://newyork.craigslist.org/mnh/roo/1295229177.html
I understand that this type of thing may not be for you or anyone else for that matter, but just figured I’d mention it. Obviously for something like this to work, the boundaries and expectations on the part of both parties must be discussed in great detail, but when it does work, it is mutually beneficial for all concerned.
A few years ago, I came across a situation with an elderly woman whose adult son had made arrangements with a young college student whose duties consisted solely of just being there every night—nothing more, no meals, medical stuff or anything else. In addition to room and board, the student was also being paid a small stipend.
Obviously something like this would not be workable for someone into drinking, drugs or unreliable. But that’s basically the “cost” of the free roof over ones head. If one has good references and a clean background check, there are many opportunities of this type. The demand is far greater than the supply.