In my experience in Montgomery County these second floor projects for bungalows start at $200,000 and go up from there. Required are new floor joists, continuous load path to footings, staircase, insulation, windows, all to current code standards, plus new heating /ac zone, new bathroom plumbing, often lead mitigation in the old house, it all adds up, square footage is not a good measure since these things are all required regardless of size. Prince Georges County may also require sprinklers.
-Paul

Thanks Paul, that's exactly the information I was looking for!