Dan Gilbert owns more than 9 million square feet of Detroit, and thinks he can develop good business out of every inch.

The Quicken Loans chairman and Cleveland Cavaliers owner has invested $1.3 billion buying and renovating buildings in Detroit's scarred downtown business district. That adds up to more than 60 properties in a city whose decades-long decline recently culminated in the largest municipal bankruptcy in U.S. history.

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"We've made a significant investment in downtown Detroit," Gilbert told CNBC's "On the Money." The billionaire has moved more than 12,000 workers into historic buildings he's purchased at low prices.

Detroit and the rest of the Rust Belt's regional economy was particularly hard hit by the financial crisis, and solidified the Motor City's status as a symbol of urban decay. The city itself is pruning its debt load as part of the an agreement struck with creditors in the wake of its bankruptcy filing.

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Still, the Cavaliers' owner thinks the city can rise from the ashes.

"There's just a bullish feeling," Gilbert said about Detroit's renewed prospects. "The costs are lower, we have an educated workforce," he said. A movement of young people to the urban core of the city is a blueprint for cities across the U.S., he added.

Gilbert's Rock Ventures is the umbrella entity of more than 100 companies. These include Detroit Venture Partners, which funds young companies in the Motor City, and Bizdom, an entrepreneurial accelerator in Detroit and Cleveland. It's all part of his billion dollar bet on America's cities.

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"You can not only do great things for an urban core by moving your employee base there, you're also going to be a better business," Gilbert said.

"It's hard to measure with spreadsheets, (but) I can tell you that our business would not be the business that we are spread among several buildings in the suburban area."

Even as the city moves to shed assets after years of decline, Gilbert is optimistic about Detroit's human capital.

"There's an energy in an urban core that you just don't get anywhere else."