New York is an expensive city...but tons of fun. I lived there for 4 years and absolutely loved it. Some advice -- renting is expensive and quick. You need to be ready to make an offer on a flat the same day you see it -- especially if it is a good deal. Most flats are shown by brokers (a fancy name for estate agents) who charge about 15% of the yearly rent. It is outrageous but often unavoidable. We managed to find out flat without a broker (Eberhart Brothers is the management company) but most of their buildings are on the upper east side. If you want to live in the real trendy areas, a broker is almost a must. The fee is on top of a deposit and first months rent up front.
As for the work permit, can't help you with that but I know there are NY lawyers who specialise in getting work permits and green cards.
Good luck!