The deal is likely to lead to profound changes for many of the 25,000 residents of the two complexes, where two-thirds of the apartments have regulated rents at roughly half the market rate. Any new owner paying the equivalent of $450,000 per apartment is going to be eager to create a money-making luxury enclave, real estate executives say.

The sale would only add to the seismic cultural shifts already under way in New York City and especially in Manhattan, where soaring housing costs have made the borough increasingly inhospitable to working-class and middle-class residents. It would be another challenge to Mayor Michael R. Bloomberg’s effort to stabilize and expand the number of affordable apartments in the city.

“It’s really sad,” said Suzanne Wasserman, a historian and filmmaker who has lived in Stuyvesant Town since 1989. “New York has always attracted people who aren’t just interested in money — people interested in culture and poetry and music and dance and those young people who are the creative capital of the city. They aren’t going to have a place here and probably really don’t already. I think it affects everything about city life.”

Rumors of an impending sale began circulating among residents several years ago when MetLife was in the midst of $300 million in upgrades that included new landscaping and playgrounds, spruced-up fountains, new wiring, air conditioning, carpeting and lights. Rose Associates took over management three years ago.

At the same time, MetLife sought to oust tenants not listed on leases. And as rents for more apartments hit the legal threshold of $2,000 a month, MetLife has been able to charge new tenants market rates for those apartments when they became vacant. Under that threshold, the rent stabilization law limits increases to a fixed percentage each year for about a million apartments. About 27 percent of the tenants at Peter Cooper and Stuyvesant Town are now exempt from it and pay market rents.