Ben Franklin Institute will move to Dudley Square

The old Harrison Supply site will become the Ben Franklin Institute of Technology’s new campus.Pat Greenhouse/Globe Staff/Globe Staff

After more than a century in the South End, the Benjamin Franklin Institute of Technology is heading to Dudley Square in Roxbury.

The technical college, which has been on Berkeley Street since its founding in 1908, on Monday completed the purchase of the old Harrison Supply Co. building on Harrison Avenue, near Melnea Cass Boulevard, where it plans to build a new campus on seven-tenths of an acre in the next few years. The school said it will soon file plans with the Boston Planning & Development Agency for a building of about 85,000 square feet.

The move will give the school a modern campus, said its president, Anthony Benoit — one that’s closer to the neighborhoods where many of its roughly 550 students live, and to nonprofits and educational institutions with which the school partners.

“Dudley Square was high on our list from the start,” Benoit said, describing the school’s search. “There’s so much going on there, and a lot of thought about how to do really great economic development.”

The purchase is part of a two-step transaction for Benjamin Franklin, which in January hired brokers to sell its South End property. No deal has yet closed for that site, which is expected to fetch tens of millions of dollars. But Benoit said there has been strong interest and he’s “fully optimistic” a sale will happen, with the proceeds being enough to pay for the new building. Any money left over would go toward bolstering Benjamin Franklin’s endowment of about $4 million.

“We’re a small nonprofit college educating low-income kids,” he said. “We need every dollar we can get our hands on. We’re pretty comfortable moving forward.”

The college paid $6 million to buy the site, according to a deed filed Monday in Suffolk County. In January, a Wellesley holding company paid $3.45 million to buy the unused building from its longtime owner.

Benjamin Franklin, founded with a bequest from the Boston-born founding father, is the latest in a wave of colleges and universities aiming to cash in on the city’s hot real estate market. But while some of those institutions have sold what is essentially surplus real estate or partnered with private developers to enhance their campuses, Benjamin Franklin is picking up stakes and moving.

That, Benoit said, meant finding a location that made sense. It wanted to stay in Boston, have about an acre to build on, with access to public transit, and, ideally, be closer to Dorchester, Roxbury, or Mattapan — neighborhoods where many of the students live. School officials and staff members toured potential sites in Dudley Square, he said, and it felt like home. The new site is about 1.1 miles from the current campus.

“We kept seeing people we know. Like, ‘Oh, there’s so-and-so,’ ” he recalled. “That’s where our students are.”

And in a few years, that’s where BFIT will be, too.

The institute put its South End campus on the market earlier this year.David L. Ryan/Globe Staff/File/Globe Staff