The fire started just after 7 a.m. in the 4600 Brockton Drive in northeast Raleigh.
At one point, flames could be seen shooting through the roof.
Firefighters believe someone lit a couch on fire in the back of the home.
No one was hurt, but at least two units were seriously damaged.
Raleigh police and the ATF are investigating.
There were no reports of injuries.