John Hantz is a wealthy money manager who lives in an older enclave of Detroit where all the houses are grand and not all of them are falling apart. Once a star stockbroker at American Express, he left 13 years ago to found his own firm. Today Hantz Financial Services has 20 offices in Michigan, Ohio, and Georgia, more than 500 employees, and $1.3 billion in assets under management.

Twice divorced, Hantz, 48, lives alone in clubby, paneled splendor, surrounded by early-American landscapes on the walls, an autograph collection that veers from Detroit icons such as Ty Cobb and Henry Ford to Baron von Richthofen and Mussolini, and a set of Ayn Rand first editions.

With a net worth of more than $100 million, he’s one of the richest men left in Detroit — one of the very few in his demographic who stayed put when others were fleeing to Grosse Pointe and Bloomfield Hills. Not long ago, while commuting, he stumbled on a big idea that might help save his dying city.

Every weekday Hantz pulls his Volvo SUV out of the gated driveway of his compound and drives half an hour to his office in Southfield, a northern suburb on the far side of Eight Mile Road. His route takes him through a desolate, postindustrial cityscape — the kind of scene that is shockingly common in Detroit.

Along the way he passes vacant buildings, abandoned homes, and a whole lot of empty land. In some stretches he sees more pheasants than people. “Every year I tell myself it’s going to get better,” says Hantz, bright-eyed, with smooth cheeks and a little boy’s carefully combed haircut, “and every year it doesn’t.”