Does the whole thing really need to be in use? What about fixing what MUST be fixed [[roof, water, electrical....) clean her up, install the windows, rehab the first and whatever other floors you need, then seal the rest up. Leave only minimal power for heating in important areas, maybe to light up a few windows in the upper floors for looks, maintenance access, etc...
If more investment comes as a result, you open up floors as required.
When people start investing in Corktown again, everyone is going to kick themselves for letting such a tresure meet the ball.