The multifamily acquisitions market became a buyer’s market as early as the beginning of last year. Cap rates for apartment properties have now slid back down to levels last seen in the mid- to late-2000s. For example, cap rates are 5.5 percent in certain California locations and in New York City, says Nathan Collier, founder and chairman of the Collier Companies. Collier spoke at a session last week at the National Association of Home Builders’ International Builders’ Show. Speakers at the session, which addressed the acquisition of multifamily properties, suggested that rising interest rates (which have increased by as much…