This. A finished basement should simply double the price of a house.
500 Sq ft (?) Garage with two cars...keeping my street and driveway clear. Room for bikes on the wall and power tools mounted on hooks. A big rolling tool chest for mechanical tools and a rack for yard tools. A shelf unit for oil cans, chargers and car wash products (junk and stuff too).
Man-cave is underground and the most perfect room in life.
My garage/mancave is underground. Goes into the downstairs den which has a full bathroom. Low ceilings make it easy to heat and its always cool in the Summer. I seldom go upstairs except to sleep.