Five U.S. states – Virginia, Arizona, Connecticut, New York and Washington – filed an antitrust lawsuit against Zillow Group and Redfin alleging an illegal agreement to stifle competition in the online rental listing market. The lawsuit was filed in federal court in Alexandria, Virginia, the same court where the U.S. Federal Trade Commission (FTC) recently filed a similar case. The big picture: The complaint centers on a February deal where Zillow paid Redfin $100 million to stop running apartment advertisements and remain out of the large-apartment-building rental market for nine years. Under this pact, Redfin agreed to display only rental listings that Zillow already featured on its platform. Zoom in: Renters currently occupy nearly 49 million units in the U.S., representing over 30% of all housing nationwide.