You could always try a few of the office parks around the different cities and bring them a lunch option. There are several along the ND tollway, i.e. Hall office park. Find a manufacturer (or two – there are dozens and dozens) on I-75 that has second and third shifts or one without a vending area or cafeteria. The farther north you get towards Sherman Denison, the more industrial areas you’ll find. In fact, Sherman and Denison may be very cart friendly. I don’t know as I’ve never approached them. Both may be ideal for setting up a daily spot.
I would certainly try to petition the McKinney downtown association for a spot on the square with the approach that a regulated street food scene only increases and retains foot traffic. If you can keep more customers on the street, doesn’t that have the potential to increase retail sales? the , too may take some work. I’d talk to the downtown merchants and get their input and/or support.
The argument will be that you’re taking revenue away from local eateries when in fact a $2.50 hot dog is not competition to a sit down restaurant. The other alternative would be another food option like pretzels, bagels, elote, or other “snack” foods.
Tell us which cart you bought and what your cart’s capabilities. That might prompt more ideas.