Is it legal to wholesale real estate in NY

It is not illegal, however, the contract would have to give you the right to assign it and whoever you assign it to may have difficulty getting financing as a result. It can be done. Your attorney would need to know all the details in advance and get it worked out so that you can assign it. The problem is that if the seller knows you can assign it to someone else for more money without putting any improvements into the property why would he sell it to you? He could sell it directly to the end user for more money. This is why most contracts say that they can not be assigned without the sellers express written consent.

Yes. It sounds like you went to some real estate flipping course, but most buyers aren't going to like paying you a premium for nothing, so I would suggest another money-making idea.

The devil as they say is in the details. Yes, assigning a contract can be done, BUT the contract must allow assigning. See a lawyer before signing any contract for the purchase of real estate. that contract is the most important piece of paper you will sign.