Every Thursday on a busy intersection in downtown San Francisco,

you'll find a bunch of young professionals waiting in line to buy food out of a truck.

In a financial district that has struggled to recover in the past few years,

this food truck,

called Senior Cisig, is a beacon of economic progress.

It distributes $15 burritos with lightning speed

as its propane power generator hums along at maximum power.

Trucks like this are now a common sight across American cities.

These mobile restaurants sell every kind of food imaginable.

Tacos, pizza, fried chicken, vegan grain bowls, barbecue, Thai, Indian, Burmese, even cupcakes.

Some of them have devoted fans who track them on the internet or seek them out every lunchtime.

The trucks pop up for a couple hours then disappear,

leaving behind nothing more than an oil stain and a tumbleweed of discarded wrappers.

When did we start getting so much of our food for mobile kitchens? What's it like to cook in one?

And is a popular food truck a gold mine?

I think there's a stereotype a lot of people will say there's no overhead in food trucks so you're just rolling in the dough and that's very far from the truth.

For the Freak economics radio network, this is the economics of everyday things.

I'm Zachary Crockett.

Today, food trucks. Serving food on four wheels is not a new concept.

Food trucks go back to the wagon train of people coming west and having to feed people out of one of the stage coaches.

That's Matthew Geller. He's the founding president of the National Food Truck Association.

It's a trade group that represents mobile food vendors across the US.

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