In L.A., thousands of newer apartments have rent caps. Tenants don't always know.

The apartment building at 5800 Harold Way in Los Angeles is under rent control. Most people assume rent control in L.A. applies to buildings built before 1978 but because of a relatively unknown city law, there are thousands of new buildings that also have rent caps. Alexa Castelvecchi was glad when she and her roommates found their new apartment about a year ago, in a modern building in Hollywood with a big, sleek kitchen and oversized windows. It was nothing like the aging, rent-controlled apartment she once sublet in Venice,...