Single fam House not Completely Converted to Duplex- Will it FHA?

[Eliza Alexa]

Single family 2 level home, separate electric meters, separate HVAC. However, to enter the upstairs unit one must access front door which opens into the downstairs living area. Can this area be walled off to create a foyer entry so that downstairs has it's own door to exit their living area into the foyer in order to access front door leading outside & upstairs unit would have access to foyer by coming down the stairs to the foyer to access front door leading to outside also? Must this be converted to true duplex if so how??? Will FHA 203k allow this, how does one make this happen & what rough price range to expect?

It seems like an uncomplicated process in theory but then again- I know NOTHING about construction/FHA or even investing except what I learn on BiggerPockets.