Ten percent of a 163-unit apartment complex planned for the former Sentry auto dealership on Mystic Valley Parkway in Medford will be designated as affordable housing, marketed to low- to moderate-income earners.

Criterion Development Partners of Texas has agreed to set aside the units to boost Medford’s affordable housing stock, said Lauren DiLorenzo, the city’s community development director.

“We asked if they would consider including it, and they agreed,” DiLorenzo said. “Whenever possible, with new developments, we attempt to negotiate an affordable component.”

Criterion has not estimated the development cost of the project, or how much market-rate rents will cost, DiLorenzo said.

“They won’t be inexpensive,” she said. “Affordable units can still be fairly costly. . . . We’ll have to see what the rents are.”

‘Affordable units can still be fairly costly. . . . We’ll have to see what the rents are.’

Heather Culp Boujoulian, Criterion’s vice president for New England, did not return calls seeking comment for this story. Robert Abruzese, a Medford lawyer representing Criterion, also did not respond to a request for comment.

Criterion plans to tear down the long-closed auto dealership, located on Route 16 across from Meadow Glen Mall. A five-story building, which includes an underground parking garage with 216 spaces, would be built in its place. A clubhouse and two courtyards are also planned. Apartments will include 33 studio units, 75 one-bedroom units, and 55 two-bedroom units, officials said. The Board of Appeals voted unanimously, 3 to 0, on May 29 to approve site plan review for the project, and zoning relief to allow residences in an area zoned for businesses. “They made a wonderful presentation,” said Anthony Arena, the board chairman. “The design and landscaping is impressive.”

Arena said Criterion’s decision to include affordable housing was not a factor in the approval. “The city addresses that up front with them,” he said. “When the project gets to us, their decision, or not, to comply is not a consideration for our board.”

The affordable units will be developed under the Local Initiative Program, a provision of the state’s affordable housing law. It allows communities and developers to collaborate, if a city or town has not met the state’s goal that 10 percent of its housing stock be deemed affordable. Medford now has a 6.8 percent affordable housing rate, state data show.

The affordable units would be available to people earning 80 percent or less of the mean income for Greater Boston. For a family of four, that figure now is $66,150, according to the city’s affordable housing website.

DiLorenzo said the state guidelines will determine the rents for the affordable units. “That will tell us what the maximum is that can be charged,” she said.

The project overall will boost the city’s housing stock, she said.

“I think it’s a great project that’s going to define’’ that area, she said. “It begins to tie into a residential neighborhood. It has great access and public transit.”

Criterion, which has a local office in Bedford, has six apartment complexes in Massachusetts, including the Residences at River’s Edge in Medford. Others are located in Andover and Winchester.

In Medford, the construction schedule isn’t clear. The developer must wait until an appeal period expires on June 26 before it may apply for a building permit.

The amount of the permit will be based on the project’s cost. “We don’t know how much that will be,” said Paul Mochi, the city’s building inspector. “It will be significant. This is a large project.”