Beware of spending upwards of $1000 on such services as you will generally end up being listed in the NY State MLS or the Long Island MLS, both of which are irrelevant to NYC. While there is a Manhattan MLS, it is not very popular vs. REBNY which has over 16,000 members.
Moreover, some of these larger “for sale by owner” websites clearly do not work, and absolutely will not work for NYC. The reason is that listing with them will be the same as listing FSBO. Not only will local brokers recognize the FSBO broker (which sometimes shockingly enough even has the word “for sale by owner” or “FSBO” in their company name), they make it even easier by sometimes syndicating their listings as a FSBO listing to sites such as Zillow, complete with watermarked photos of their FSBO company name. Ironically, there are services such as BrokersMust that actually sell lists of these FSBO listings to hungry brokers looking for new clients.