LOS ANGELES—Renting an apartment in Southern California is about to get much more expensive. A USC Casden Economics Forecast released on Nov. 9 predicted sharp increases in rent across the region, with Orange County renters seeing an average monthly jump of $410 over the next two years. “COVID-19 caused a large-scale move from central cities to the suburbs that resulted in a sharp rise in apartment vacancies in Downtown LA, Koreatown and Beverly Hills and historically low vacancies in Rancho Cucamonga, North City San Diego, and Oxnard,” said Richard Green, co-author of the forecast and the director of USC Lusk Center for Real Estate. “While vacancies are coming back down in urban areas, the outskirts remain low [in] supply and will see rents go up at a much higher rate than the cities,” said Green. The forecast predicts that by the end of the third quarter in 2023, rents will increase by $252 over the current level in Los …