My main question is  : is it possible (and then how) to use a complete CT as a template for a specific custom type ? Does it implies a specific Folder app structure ?

I think it's because i don't undersdand the full potential of Apps Folder but, how - and i mean step by step if possible - use the App Folder structure :

For instance, i'd like to do a real estate website, "simple" in the beginning but that could be complexified if needed, so i have to have a good logic about it's creation.

I need some generic field (title, description, price, reference, images..), and some specific fields wether it's a location or a purchase (rent, service charges for location and total price, monthly payment).

So my first question is : 

For this structure, should i have 

Folder app : Real Estate . Then should i create sub folders for the different types : => renting / purchase ?

I would like to have the generic fields in a generic content type "Product", and then when i create a content type "Renting", i could use the "Product" content type fields and add my specific renting fields. It would be the same for "Purchase" CT : use the generic Procuct CT, and add the specific ones.

My second question is : 

To achieve that, should i set specific setting on the Folder App (=> App Root or not ? Featured or not ?)

Or is it only by using exculsive/non exculsive (lock/unlock) fields i can reuse generic fields ?