I have done several projects over the years.
#1 Expanded a mountain cabin into a home by a factor of 3x.
4 room cabin ( no bathroom ) was expanded into 8 room home.
One bathroom , very large living room , huge 2nd floor bedroom, utility room added.
#2 Duplex expanded from 400 square feet on each side to 800 square feet on each side plus deck in back.
#3 Added Apartment to house, opened it up and added loft bedroom. 800 square feet expanded by 200 feet on main floor plus 400 square foot loft. added two bathrooms.