Condo Conversion for SF

Hi all,

Hope everyone is having a lovely day.

I have a friend asking about condo conversion stats for SF.  She is interested in buying a duplex and converting but wants more info about appreciation values, costs, etc.  I can tell her what I know but it is anecdotal coming from me. 

Does anyone know of a more verified source for this?  Even what you know will be helpful if you had experience or know-how of this. 

Much thanks,