You should think about how long you expect to live in the City and if your initial investment can be recouped. You also need to work with a Realtor who keeps up with the market trends. Keep in mind that no one can predict the future, but you can get help in determining if you're over-paying, based on the market when you purchase. If you're not acquainted with Manhattan and Brooklyn neighborhoods, I suggest visiting and perhaps renting for the 1st year, waiting to purchase until you feel more knowledgeable about the local market and the neighborhoods.
I'll be in Lincoln, NE the last week in July. I would be happy to meet you and provide you a Manhattan Buyer's Guide or market statistics OR I can email both to you. Good luck.
These guys might be a good start: