DETROIT—Locals call it the "Dan Gilbert effect," the recent buying spree of commercial buildings in downtown Detroit by the billionaire founder of Quicken Loans.

Now the phenomenon appears to be spreading.

Despite a fiscal plight that forced the city to seek Chapter 9 bankruptcy protection five months ago, the real-estate market has been picking up in Detroit's downtown core. Mr. Gilbert has led the charge by buying dozens of properties and moving in 3,800 of his employees from suburban offices and creating another 6,500 jobs downtown since 2010, according to the company.

But lately, other investors have begun buying trophy buildings and starting to develop apartments to meet the rising demand from workers who prefer downtown living. City officials estimate residential occupancy downtown is 97 percent.

The projects show that some real-estate investors are looking beyond the bankruptcy to an eventual rebound in Detroit. They are hoping that property values and rents will rise due to the region's resurgent automotive industry and the expansion of its medical community and nascent technology industry.