CAPE CORAL, Fla. — After an improbable rise from the Bronx projects to a job selling Gulf Coast homes, Isabel Bermudez lost it all to an epic housing bust — the six-figure income, the house with the pool and the investment property. Now, as she papers the county with résumés and girds herself for rejection, she is supporting two daughters on an income that inspires a double take: zero dollars in monthly cash and a few hundred dollars in food stamps. With food-stamp use at a record high and surging by the day, Ms. Bermudez belongs to an overlooked subgroup...