What is your process for adding rooms to a SFH project?

[Wesley Wilk]

Morning! I'm not a real estate investor, but I like learning. I'm currently reading David Greene's book on BRRRR and was curious about how you all go about planning or visualizing added rooms to potential purchases.

I went on Zillow and found this 1900 square foot house with 2 bed, 1 bath and a nice floorplan in the listing. Its an old house that would need a renovation, so I was thinking about how I would add rooms to it and realized I'm pretty clueless about it.  What would your thoughts be on adding a bedroom and bathroom to this floorplan without expanding square footage?  OR is this something you would take to your favorite contractor and ask them to come up with a plan? Or maybe a little of both? 

Appreciate your input.