I'd start with local and state laws. Health codes and Sanitation, tax stuff and you might want to search for any exceptions and exemptions for mobile operations and for sweets. Sometimes serving only nonPHFs gets you a break.
Not sure how far you are into the planning phase of your venture.
Are you describing a food truck that has a cookie focus?
If you want to go nuts and have some fun, use a portable wood fired oven...
I'm sure someone else will come along with better info.