Rear/back split extension on bungalow

I have a bungalow size 25x45 (very small rooms, 2 bedrooms, living room, bathroom and kitchen on main floor) and looking to see what it would cost to build back extension or do a back split to create a additional bedroom upstairs with bathroom and living room on main floor with sliding doors to backyard. Lot size is 25x149.5 it is a mutual driveway, neighbors park car in front and we park our car in the back. Ideally I would like to get a permit for front parking and utilize the back parking spot as the extension on the home. Parking pad is 25x15 give or take. Picture is the parking space that is directly from back door of house. Open to other suggestions/ideas on how to make this tiny home a regular size home.