It's questionable if you're going to get any profit at all when you have to pay someone to man the store at odd hours when there's almost no customers. A few people coming in during the late-night shift and buying $3 worth of stuff each is not going to pay that employee's salary.

Have you read the article? The franchise pushes the store owner to make it work anyway, and since the employee's salary would eat his profit, he cannibalizes his free time and sleep instead. The franchise contract is probably structured in a way that the franchise company profits even from stores that are themselves barely profitable.