Before moving from their traditional home in the suburbs, Terry Cracraft-Antin and her husband, Alan, purchased a raw space on the top four floors of 909 Walnut, a former bank building located in downtown Kansas City, Mo.

The 6,000 square feet of unfinished space took 2½ years to build, costing about $3 million, said Ms. Cracraft-Antin, who declined to disclose the purchase price. The couple, who have four adult children, now host cocktail parties in a billiards and bar area that overlooks their private rooftop terrace or...