Your "carriage house" with a skylight may well have been built as a
photographer's studio. There was such a building (with the skylight close
to vertical on the north wall of the second floor) in the Mount Vernon
neighborhood of Baltimore--presumably it is still there. I found it 20
years ago when I was a photography student at the nearby Maryland Institute
College of Art. A professional photographer I told about tried to rent or
buy the place to set up a studio, and found the owners totally uninterested
in what they had. Too bad.
Don White