ARLINGTON, Va.--(BUSINESS WIRE)--Today Apartments.com, an industry-leading online marketplace of CoStar Group (NASDAQ: CSGP), published its latest report on multifamily rent trends for September 2025. U.S. apartment rents declined in September, with the national average falling to $1,712 — a 0.3$1,717. This marks the third consecutive month of flat or negative monthly rent change and the steepest September decline in over 15 years. Annual rent growth s. ...