Twenty percent of the housing units constructed on a 5.5-acre development on state-owned land blocks from South Station must be affordable if the prime parcel is going to be redeveloped as part of a statewide program aimed at selling and leasing unused and underused state-owned land.

Builders looking to redevelop the land on Kneeland Street — where the state Department of Transportation’s District 6 offices now sit — will have to include enough affordable units to satisfy Boston’s requirements for developments and an additional state requirement pertaining to workforce housing.

In addition to satisfying the requirements, developers will also have to upgrade and maintain an existing park and basketball court, state officials say.

“The community would like to see useful open space, both passive and active, as well as significant affordable and workforce housing units,” the state’s request for proposals said. “For any housing that is developed on the property, an increased percentage of affordability, beyond the city’s inclusionary development policy will be required.”

Bids for the property are due by March. The plans must be at least $167 million, replace the DOT district office and rebuild a steam plant that heats part of downtown. Still, Gov. Charlie Baker said the project requires striking a careful balance between increasing revenue for the state and improving housing and open space — particularly in an attractive neighborhood for high-end real estate.

“It’s a constant balance to try to figure out how to make sure we’re getting what I would describe as the best dollar for the investment,” Baker said.

The Kneeland Street project is one of 85 pieces of state-owned land that will have been offered to Bay State developers as part of an initiative to put vacant state lots to use. Of those, 22 have already been sold or leased.

“There are 80 projects that are currently underway, in about 40 or 50 communities in the commonwealth,” Baker said, “with the potential, I think over time, to put a lot more unused, non-revenue generating and in some cases just downright eyesores in communities to work.”

The projects include 37 solar canopies over MBTA parking lots that will generate yearly rent for the state starting at $1.9 million, and increasing each year.

Other properties that are being targeted include 44 acres in Worcester at the former state hospital campus and a plot under the Neponset River Bridge in Quincy that is being leased to a company for parking. The 22 properties are expected to generate $413 million in revenue for the state, along with more than 1,500 housing units.