(Mark Your Calendars: RealShare Apartments 2011, October 20 in Los Angeles).

CHICAGO-Three towers in the $850 million K Station apartment complex are now up for sale. The owner, a joint venture of locally based Fifield Cos. and Newport Beach, CA-based Pacific Life Insurance Co., is testing the frothy apartment market waters with the 1,198-unit Echelon and Alta, located in the West Loop, with an asking price of $475 million.

At 353 N. Desplaines St., the 350-unit Echelon tower is 95% leased. The tower includes studio, one- and two-bedroom units ranging in size from 572 to 1,111 square feet, and rents from $1,565 to $2,845 per month.

There are two towers at Alta at K Station, which is 87% leased at 555 W. Kinzie, according to an owners statement. The 37-story, 420-unit West Tower and the 41-story, 428-unit East Tower have been open since June 2010. The towers have studio-, one- and two-bedroom units as well as penthouses, ranging from 508 to 1,807 square feet and with rents starting at $1,455 per month.

Steven Fifield, president of the self-named firm, said in a statement that because of the lack of new construction and the extreme low vacancy rate for apartments, the time is right to sell. “The apartment market is very strong right now. It’s the hottest asset class around and these two buildings are high-performing rentals,” he said. He was not available for comment.

A recently released third quarter apartment market report by Marcus & Millichap bears him out. With vacancy on track hit less than 5% this quarter, expanded financing and only 700 units delivering this year, there should be a healthy flow of deals, according to the report.

The K Station complex should be one of the top properties available. Amenities include a one-acre park, a 48,000-square-foot amenity deck with a sports court, resident lounge, party suite and private balcony, a business center, theater, a fitness center and locker rooms, an outdoor sun terrace with a pool, spa and private cabanas and a gourmet grill kitchen. A Blue Agave Restaurant and Tequila Bar is opening in 6,000 square feet on the ground floor this fall.

John Jaeger and Dan Cohen with CB Richard Ellis are representing the owner in the sale. A CBRE spokeswoman says the buildings are offered together or separate, with an asking price fo about $400,000 per unit.