Urban farming = Job growth?

I recently read about plans to change Detroit's zoning to permit urban farming on the Mother Nature Network. I'm all for urban gardening/farming, but I increasingly find that I am questioning the rationale behind it:

...

In Detroit, where zoning laws ban growing crops and raising livestock for profit, city planner Kathryn Lynch Underwood is part of a work group rewriting the regulations and defining what kinds of urban farms might need more oversight.

"The city has not been treating it as an illegal use or a nuisance because it has been a good thing," Underwood said.

She is hopeful that urban agriculture and the city's nearly 1,000 community gardens will create good jobs in a city that desperately needs them and put vacant lots to use in blighted neighborhoods.

...

 (You can read the full article here:
http://www.mnn.com/food/farms-gardens/stories/urban-farmers-fight-to-sow-green-biz)

This leaves me wondering, just how will small inefficient farms/gardens "create good jobs in a city that desperately needs them"? Farming has been notoriously unprofitable and often pays among the lowest wage scale.

According to a study done by Rene P. Rosenbaum, Associate Professor Department of Resource Development, at Michigan State University [pdf], residential seasonal farmworkers in Lenawee County earned $5,057 on average in 1996. I think it is fairly safe to assume that anyone creating an urban farm is likely to employ residential seasonal workers (if anyone) or migrants, which according to the same survey earned $2,228 for the season. These are clearly not "good" jobs, and they're only seasonal at that.

Often it seems that environmentalists are considered blasphemous if they say anything negative about urban farming.  Particularly because there are wonderful programs like Capuchin's Earthworks Urban Farm that provide a terrific service (and food!) on a non-profit basis.  However, for-profit, large-scale, urban farms strike me as a sort of goofy response to the food deserts that are many of our urban centers.  Is farming in the middle of a city really the best use of that land? I know the argument is that the blighted land is not being used now and it’s a wasteland of urban decay, so why not? Farming would certainly fill that land. I don't really have a good response to that, but the point is that farming is not an economic solution.  It is simply a subsidized solution to filling vacant space.

My grandfather's roughly 170-acre farm in rural Iowa was sliced up when a road was needed as Des Moines sprawled, then cut in half again when the gas company decided they needed to run a pipeline through it in the mid 1990's. After several years of court battles, his farmland was cut into three distinct chunks with strips that could not be farmed because they were claimed by eminent domain for the state and gas company. If we as a country can't keep from splitting up farms in Iowa, what kind of convoluted thinking leads to believing that a farm in an urban center is going to remain intact after the next resurgence of Detroit?

I think encouraging urban farming/gardening as supplemental income or a hobby is a terrific contribution to the need for more fresh veggies in urban centers and as an educational tool for kids. Moreover, I completely agree the zoning laws should be fixed such that urban gardens can be planted, produce sold at markets, and the owners not put themselves at risk of being hauled into court battles. However, expecting it to be a source of "good job" growth or that these could be profitable, generational farms strikes me as borderline delusional.