What are the steps for a sfh to a multi fam conversion for NYC

[Malcolm Hyman]

Hello, im currently in the process of converting my SFH into a two family, The home is zoned in a two family location. I just wanted to know the steps to getting everything done appropriately. I called a architect and he quoted me $25k for plans that he mentioned i need, but i have no way to verify if its needed or if im being taken advantage of. A website or document that spells everything out would be really helpful.