Detroit's reliance on casino cash to help fund a recovery from the city's historic bankruptcy is a high-risk bet on an increasingly shaky source of income.

A trial to approve Detroit's plan to exit its $18 billion bankruptcy, the largest municipal crash in U.S. history, will begin in late July. Flawed revenue projections may undermine its feasibility, creating a key legal hurdle to win approval by the court.

On a practical level, a revenue shortfall could knock the city down just as it is getting back on its feet.