The best way to invest a single dollar

> Growing coffee isn’t hard. It’s the time-consuming extraction of the beans that defeats would-be backyard growers.

> Every season when the coffee bushes hidden in the shade of the Wattles Farm community garden in Hollywood start to produce cherries, one of the gardeners volunteers for the process of peeling the shells, removing the fleshy pulp along with the interior parchment, and washing and air-drying the tiny beans within.

> “They’re very enthusiastic in the beginning and are still enthusiastic at the end because the coffee is very good, but they swear they’ll never do it again,” said Laurel Delp, one of the gardeners at Wattles.

Also, according to that romantic notion:

> A dollars’ worth of seeds will result in a conservative estimate of 60 plants. Each plant yields 10 pounds of coffee cherry per year.

That assumes a full-grown tree. From http://www.coffeefair.com/coffee-facts-plant.htm :

> Do you have the patience to wait for three or four years? Well that's about how long it will take you before you can harvest your first beans from your own coffee plant. ...

> Coffee plants will produce fruit without any fertilizing whatsoever, but for best results and maximum yield, they should be fed every 2 weeks from March to October, and then monthly from November through February. Use a soluble, all purpose (10-10-10) fertilizer.

As you say, the land, water, fertilizer, and time to farm and process the plants, and delivery costs, are all assumed to cost nothing.