The front-runners for the democratic presidential nomination may disagree on health care and tuition-free college, but they share one thing in common: a good nose for real estate.

In South Bend, Ind., a 20-something Pete Buttigieg snapped up a foreclosure in a historic neighborhood for $125,000 in 2009; the home is now worth nearly twice what he paid for it. In Wilmington, Del., former Vice President Joe Biden and his wife Jill Biden spent $350,000 to buy a lot on a manmade lake; now, real-estate veterans say the home they...