While food sales to your door may be convenient, meat sold at your door may not be safe. Reports have been made in other states of meat being sold out of trucks or backpacks. Reputable vendors will have a license to prove their business is reputable.
Lack of refrigeration on the truck is a red flag that the vendor is illegal. Outdated meat or no labels on the packages is another concern.
Some other ways to determine if the vendor is legit is to ask for literature that lists a sales office with contact information. Read the label and look for an establishment number for USDA meat inspection. Look for a grade shield on the package for quality. Ask for a retail permit or State license.