Well in my case I am in SW PA. The outbuilding has been a woodworking shop and none of the tools have ever rusted so humidity is not a huge issue.
Space in the house is not an issue either as I figure I can take and build about a 15x12 foot room in the basement and never miss the space.
Basement is not totally underground so it is not a damp dungeon. The front is actually ground level. I also have the means to make my own siding
to finish the walls and make it a very nice den. The whole 30x50 foot basement will be my domain so I don't have to make the mrs. happy.