If Barbara Butler looks down on her clients, that's only because most of them are shorter than she is. And typically a few decades younger, too. But by combining her inventive ingenuity with their uninhibited imaginations — supported by generous parental funding, of course — she has been able to turn pure play into profitable work.

Butler designs and builds custom playhouses, which range in price and complexity from a $3,300 brightly painted cabin to a glazed, wired, and plumbed $166,000 redwood chalet. Among the details kids request are slides, climbing walls, rope ladders, zip lines, and jail cells with secret escape hatches — architectural elements that ensure the occupants will get plenty of exercise, both physical and mental. Butler builds the fanciful wood structures in her San Francisco shop and ships them all over the country for installation by local tradespeople.

To view more of her perfectly playful portfolio — plus project prices — go to www.barbarabutler.com.