There is a surge of new apartment inventory starting to hit the market, most of it luxury rentals. While such buildings have had little difficulty finding tenants in the past, that may be changing, according to Zumper's latest multifamily report. 

CEO Anthemos Georgiades cautions that vacancy rates in such buildings are on the rise. The reason is that renters are scaling back due to fears about the economy, he says. "That means," he says, "these new Class A properties coming to market in many cities will have a harder lease-up period than originally anticipated, putting downward pressure on luxury rental pricing."

One exception is Miami, where new renters are disproportionately interested in luxury amenities, according to Zumper. Resort-style perks like concierge services, on-site restaurants and free fitness classes are increasingly common in Miami apartment communities.