So far as I know you cannot vend in NY, DC and other major cities without a permit. Perhaps NY has some relaxation of provisions for Veterans. In DC about 5,000 lower income street vendors were pushed out of business by collusion of big business and government with a little graft thrown in for good measure.
Since the civil war, disabled veterans have been free to vend on the sidewalks of New York, unless the last two mayors changed that.