I just returned from 5 days in NYC with 9 college students. We stayed
at the Youth Hostel (open to people of all ages) on 103rd and Amsterdam
on the Upper West Side. It's the world's largest hostel - over 600 beds.
Lots of action and people from all over the world. A great way to meet
people, especially if travelling alone! My students enjoyed that experience.
It's about $35 (or less) a night - sharing a room with 4, 6, or 12 people.
Bring a locker lock to stow stuff during the day. They have a cafe, a
gift shop, and they run great group tours. There is something going on
every day. We took a walking tour of Harlem and it was fabulous. The hostel
is less than 2 blocks from the subway - so it was very convenient. I would
suggest that your friend take a taxi to or from the hostel after dark,
if alone. Although we felt very safe at all times!