New York City, Sole Proprietor without LLC, How to obtain a Resale permit for Amazon selling ?

The state government website (it's through the state, not the city; although additional city licenses may be required) should tell you everything you need.

But I would advise that you go ahead and set up an LLC and get an EIN; it's a lot easier to start with them than to change later if you find that you need them (such as expanding to hire an employee). The cost is not that big.