GGB Five numbers: the all-in cost per trading day; realistic covers per service window at your price point; contribution per order after packaging and payment fees; the number of confirmed trading days per month you can genuinely book; and the capital ceiling you will not cross including the preparation kitchen. If those five don't hold together on paper, the truck will not fix them on the street.
From The Dubai Food Truck: Why, and Why Not — the full reading, with the method behind this answer.