In the gp's post, he's talking about above ground mounting, similar to rooftop, and more like the parking lot coverage in tfa... in this case it's actually about a break even for the solar in 8-12 years usually... (feel good qualities not withstanding)... that covers the electrical usage for the lot's residents, at the very least. Assuming you are charging for the electricity... you are still making the lot rent, and on top of that, you can charge more for being a "green" lot (if the organic food market is any indication), which means you can charge over 20-30% more than standard lots... so your break even on investment is about 8-12 years, but you'll be making 20-30% more on the lot rent, which means you'll probably break even much sooner, and see a close to pure profit for 8-10 years after the investment paid for itself.

It's not a bad system... this also doesn't account for states like Arizona and California that offer tax breaks and incentives for solar initiatives like this one.