A San Francisco developer's plan to build a 54-story office and residential tower in the city's South of Market neighborhood will cost about $375 million, according to a person familiar with details of the proposal.

Builder Jay Paul Co. plans to "immediately commence construction" of an 800-foot 244-meter high rise near the site of the city's new Transbay bus and rail terminal, the San Francisco-based real-estate firm said Friday in a statement. The building will also be near an office tower planned by Boston Properties and Hines that's set to be the city's tallest.

The 181 Fremont mixed-use tower will contain 684,000 square feet, with 74 residential units, 420,000 square feet of offices, and retail space.

San Francisco has the best office outlook of any major U.S. market for revenue growth per square foot through 2017, according to research firm Green Street Advisors. Average downtown rents in the first quarter rose 12 percent from a year earlier to $51.92, broker Cushman & Wakefield said.

Designed by San Francisco-based Heller Manus, the 181 Fremont tower "will be a very iconic building," Jay Paul, principal and founder of Jay Paul Co., said in the statement. "The unobstructed views and exoskeleton structural system that allows for column-free layouts and floor-to ceiling windows will be optimal for tech tenants."

The building's cost works out to $540 per square foot and includes $75 million for the site and approvals from the city, said the person familiar with the plan who asked not to be identified because terms of the deal are private.