As luck would have it, several models were open. They liked what they saw. As even greater luck would have it, on the way out they bumped into an agent, Kathleen Malone of @Properties, and she told them she had one unit that was a steal of a deal.

“We walked away after that just to make sure we had our figures in order and to make sure this wasn’t something we were doing on a whim,” said Mr. Warnes, 36, a project manager for a global staffing company. “But this was an offer we couldn’t refuse.”

The Laasraoui family, whose primary home is in Lugano, Switzerland, said they wanted a modern American counterpart to the slower European country life. Chicago’s downtown has been virtually reborn as a residential and arts and entertainment district over the last 15 years, and the city is a finalist to be the host city for the 2016 Olympics, a position that has only increased its international cachet.

Image Nancy Laasraoui and daughters Mariam, center, and Yasmine, spend summers in a Gold Coast condo. Credit... Sally Ryan for The New York Times

“We could have picked London, could have picked Italy or another place in Switzerland, but we like the Gold Coast,” said Abdellatif Laasraoui, 47, referring to the area north of the Magnificent Mile where his family moved into a half-million-dollar vacation condo last year. “There is no comparison in space or comfort. You’d have to pay 10 times more to get something comparable.”

“And,” added Mr. Laasraoui, an executive for a steel manufacturing company, “to commute from Chicago, it is very easy. I can go anywhere in the world from Chicago.”

Mr. Johnson, 53, the empty-nester, is actually seeking a third home, a place in to complement a lake house in Michigan and a home in La Grange Park, Ill. He wants to be able to walk to his downtown office on weekdays instead of taking a train and a bus from La Grange Park. Single after a divorce, he wants to be close to the vibrant night life of the Gold Coast and other downtown areas.