I have a 400 sq ft. room next to my carport I am wanting to convert to a granny flat.

There is electricity but no water or plumbing.

I am on a septic with city water.

How is a toilet drain line tied into the septic? Where does the water get tied into?

I realize I will need to hire this done but I want to have some idea of what needs to be done so that when the plumber is talking to me I will know if he is not trying to charge me for things I don't need.