The fire began shortly after 5:30 p.m. on Thursday, with most of the flames contained to the back of the building.
Firefighters arrived 45 seconds after the call and were able to salvage three-quarters of the building.
Living in the home were 11 adults in their own rooms, and a family in a ground-floor apartment.
The Red Cross has set up temporary housing for all residents who have been displaced.
Officials say the cause of the fire remains under investigation.