A few years ago, a Maryland-based couple started looking for a home in Maine. Their youngest daughter was living in Portland, newly married with a small baby; with three other daughters and a growing flock of grandchildren, they wanted a place where the family could come together by the water and where they could eventually retire.

The house sprawled languorously along a sandy beach and commanded a promontory overlooking blue ocean that stretched to the horizon. The shingle-style demeanor gave it a quintessentially New England coastal cottage aspect. From the outside, at first glance at least, this 12,000-square-foot, five-bedroom home on the southern Maine coast appeared to be just what this fifty-something couple wanted in a second home.