assume there is no insulation. this will be the time for skylights, a
pair of dormers, a new roof, new insulation, new windows, electrical
wiring, cable/satellite/internet wiring, plumbing. smoke detectors, CO
detectors, and a fire extinguisher. and intercom/buzzer/camera for the
entrance door. and HVAC.
if permitted by your local building inspector at your city hall.
also look there for copies of the blueprints on file. if available they
will help you very much.