The 1-alarm fire was reported at 2:35 a.m. at 670 53rd St., according to the fire department. Firefighters had it controlled by 3 a.m.
The fire had started outside of the house and worked its way into the attic, Battalion Chief Geoff Hunter said.
It cause extensive damage to the upstairs and smoke and fire damage to the first floor, Hunter said.
Firefighters also had to force entry into the building, he said. Hunter estimated total damage to the building at $150,000.
The fire is considered suspicious and an arson investigator was called to the scene, Hunter said.
There was no one in the offices when the fire broke out and no one was injured, he said.