Kendall Capital has bought 18 Tremont St., a 12-story office building across from Boston Common, for $29.5 million. The buyer, a Boston firm that makes its living turning tired offices into apartments, paid 71% less than the roughly $103 million that Jamestown laid out for the tower back in 2019. Institution for Savings, the Newburyport lender, provided $20.6 million toward the purchase.

Kendall hasn’t said yet what it intends for 18 Tremont, but its recent track record points one way. Last year, the firm picked up 320 Summer St. in Fort Point and, in May, it won city approval to carve 145 apartments out of it — one of a string of downtown conversions now moving through Boston’s office-to-residential program.

The building is a natural candidate for that kind of second life. It runs about 202,000 square feet across 12 floors with ground-floor retail, and sits just steps from Government Center, Downtown Crossing and all four of the MBTA’s subway lines. What it has been short on is office tenants — the same demand problem that has been weighing on older Class B space across the city.

The sale shows how far office values have fallen, but a low price is also what makes a conversion possible. At $146 per square foot, 18 Tremont sold for below the $184 that Boston office buildings averaged in 2025, according to Yardi Research Data. Now, the city assesses it at $49 million (down from $71 million two years ago). Plus, turning an office building into apartments is expensive, so the deal only works if the building is cheap enough to start with. Boston also offers a tax break worth 75% of the bill for up to 29 years to encourage these projects. Dozens of buildings across the city are now in the conversion pipeline, and several are under construction.