But the jury is still out on all payment solution start-ups, including Square, said the banker.

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Matt Meeker, CEO and founder of BarkBox, a site that sells care packages for dogs, shares 8, 000 square feet in Chinatown with six other start-ups.

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Neighborhoods such as Union Square in Manhattan and Dumbo in Brooklyn have become incubators for start-ups.

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Union Square Ventures, a New York venture-capitalist firm that invests heavily in tech start-ups, hired two analysts last month after a search that started last fall.

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Nonprofit 1871 on May 2 will open its doors to about 100 start-ups seeking affordable office space and a collaborative work environment in a new 50, 000-square-foot center, which is now under construction in the city's Merchandise Mart.

WSJ: A Start-Up Ecosystem Forms in Chicago