Should be easy to do however your best bet is to purchase a condo which rarely has renting restrictions. Most coops will allow you to rent for a year or two after you've lived there for a year or two. There is little flexibility in most coops and finding one with flexibility is like finding a needle in a haystack..
Starting with a good broker should be the first thing you do. He/or she can be a great asset to you in all steps of your purchase. If you're buying from abroad, your broker can send you pictures and floorplans and connect you with a real estate attorney who you can appoint as your power of attorney, unless you have someone else here in NY to appoint.
As another agent here said -- make sure you trust your broker. That is critical wether you are here in person or abroad.
If I can be of any asstance please do not hesitate to contact me
All the best,
Licensed Real Estate Salesperson
Member of Real Estate Board of New York
770 Lexington Avenue, 10th Floor
New York, NY 10065