The hot dog carts that are synonymous with New York City street food are run mostly by men. So are the ice cream stands in Central Park, and the halal carts dishing out aromatic tins of chicken and rice in Midtown.

But just as much a part of New York City life, if harder to spot, are the female street vendors, who often hawk their wares from small pushcarts. They sell things like sliced mangos on busy street corners, churros on subway platforms and Italian ices outside of schools in warm weather, usually for a dollar or two.

A video of police officers handcuffing a woman selling churros on Friday in a subway station in Brooklyn has focused attention on this subset of street sellers, who generally work without permits or permanent locations. That puts them at risk of fines, property confiscation and arrest.

[Read more: The policing of churro sales in the subway.]

Their decision to work illegally, those who study street vendors say, is linked to a broader problem: It is practically impossible to get a permit for mobile food vending in New York City, except on the black market. In that booming, male-dominated economy, $200 city-issued permits, good for two years, can easily rent for upward of $25,000 each.