Brandon Klein has done what few Floridians can: go weeks without driving his car.

The 26-year-old tax accountant walks three blocks from his condominium tower on Miami’s Biscayne Bay to his office at Deloitte LLP. On weekends, he and his friends hang out on the pool deck or share a cab to a local pub.

He lives in Downtown, a neighborhood where young people are renting condos built during the 2004-to-2008 boom to attract second-home buyers.

Thanks to the housing crash, Klein and two roommates pay about $900 a month each for an obstructed waterfront view, a wraparound balcony and access to a gym, spa and steam room.

“Five years ago, you wouldn’t have kids fresh out of college living in luxury like this,” said Klein, sitting in the three-story lobby of his building on Biscayne Boulevard, coordinating happy-hour plans by text message.

His friends are concentrated in nearby Met I, which has 447 luxury units and a steakhouse on the first floor. They refer to the building as “Deloitte Dorm” because it’s home to so many employees of the accounting and consulting firm.

The 7,000 unsold condos in Miami’s core – symbols of a building boom that collapsed and dragged the city into recession – are filling up and giving life to neighborhoods that previously closed after dark.

New, year-round residents are cramming into restaurants and nightclubs that didn’t exist a few years ago and enjoying a lifestyle made possible in part by developers and banks seeking to recoup losses by renting luxury dwellings until the market recovers.

“I’m a big-city person, and I always thought Miami didn’t have a real city,” said Dejan Krsmanovic, 39, a biomedical engineer, at Segafredo, a busy new Italian restaurant in the adjacent Brickell neighborhood.

“Miami Beach is not a city, it’s a resort,” he said. “This is beginning to resemble a city.”

The Miami Downtown Development Authority estimates that the population of Miami’s urban core jumped to about 70,000 from 40,000 since the 2000 census, authority spokesman Robert Geitner said.

“For us, it doesn’t matter whether they rent or buy,” Miami Mayor Tomas Regalado said. “The more people, the more business, the more safety, the more progress.”

The influx of college students, young professionals and empty nesters from the Coral Gables section and the suburbs intensified about 18 months ago when banks that financed the condo projects agreed to let developers slash sales prices by as much as 40 percent, said Peter Zalewski, a principal with consulting firm Condo Vultures in Miami.

That spurred demand from foreign buyers and all-cash investors, many of whom are renting out their units until prices rebound, he said.

The Miami metro rental market is one of the nation’s strongest, according to Ron Johnsey, president of apartment-research firm Axiometrics. That’s the case even though unemployment is more than 11 percent, compared with 9.5 percent nationally, and developers are adding to supply by leasing units built for purchase.

Condos are being purchased by investors and rented out in Phoenix, San Diego and Las Vegas, where thousands of units also went up during the boom, according to Ross Moore, chief economist for real estate services firm Colliers International.

“It’s something we’re seeing in many markets,” he said. “Miami is an absolute extreme example.”

While the city is heading in the right direction, it will take years to recover fully, said Michael Fratantoni, vice president of single-family research and policy at the Mortgage Bankers Association.

“Miami has been one of the areas most deeply impacted by the crisis,” he said. “But the backstop of foreign-buyer demand is going to help Miami do better than the rest of the state.”

Miami is turning into something that Florida has never had: a densely populated city where professionals live and work, said Alan Ojeda, whose Rilea Group recently finished 1450 Brickell Ave., one of three new office towers in the city’s urban core.

The $270 million building has 35 stories, 585,000 square feet of rentable space and 1,200 parking spaces.

“It’s what’s missing in Florida,” Ojeda said of Downtown. “Look, it’s 9 p.m. on a Thursday. It’s not Saturday night fever, and the bars and restaurants are full.”