What people are saying about Manhattan and a car is true. In Manhattan anywhere you can get by car you can get to faster by train. Outside of Manhattan though cars are much more reliable. A hour and a half trip by mass transit can be cut down to half an hour easy if you're in Brooklyn or Queens for example.
Weather isn't terribly complicated. Dress light in the summer and wear thermal in the winter and a sweater anywhere in between. Only thing new you might learn about weather in NY is that snow sucks.
Honestly I think you should just live close but not quite in Manhattan like in Brooklyn or the Bronx if you're just starting out. Price difference is night and day but you might still need a roommate. You'll just have more space for. Then again I've always lived in Brooklyn (except for half a year) so I might be a bit biased.
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