Best way to permit attached dwelling unit? Savannah, GA

[Charlie Anne]

There's a large 5 bedroom home I'm interested in buying in Savannah. I want to turn the upstairs into it's own unit to rent on AirBnB. Since it will be owner occupied I would be able to legally have a STR.

The upstairs has 4 bedrooms/1 bathroom. I’d like to convert the bedroom directly above the kitchen into a kitchen. The stairs to the 2nd floor go to the side of the house near the back entrance, so it would be really easy to add a wall so that when you enter through the back door you are in a small hallway that leads directly upstairs. 

I don’t think the conversion will be too costly given the layout. The room I want to convert to a kitchen shares a wall with the bathroom sink so there’s plumbing right where it’s needed. There’s already 2 HVAC units and 200 AMP electricity (house from 1900).

What's confusing me is do I need a special permit to make an attached dwelling unit? Or do I just need permits for adding a kitchen and a wall downstairs? The area is zoned for multi family, but I don't want to become a duplex. I would like to have the property remain as a SFH with an attached dwelling unit.

I see lots of people turning their basement into another unit, this seems very similar. I can’t find clear guidelines for Savannah online.

Has anyone done this before?