Authorities say the fire broke out at a one-story office building in the 10700 block of Paramount Boulevard just after 2 a.m. Firefighters arrived and found flames shooting into the air. When the roof collapsed, firefighters were forced to go into defensive mode.
No one was in the building at the time of the fire, officials said, and there were no reports of injuries.
The structure is considered a total loss, including Susana Hernandez's realty business.
"Everything's in there, all our equipment, our files, clients' information," Hernandez of Victorian Homes Realty said.
Another business that burned is a tax preparation office.
It took more than four hours to extinguish the blaze. The cause of the fire has not been determined.
Paramount Boulevard between 5th and 7th streets was closed due to the fire.