The Fire Service was called to the Kaikorai Valley Rd address shortly before midnight, after the man found his home ablaze.
Detective Matt Preece said the fire was being treated as suspicious, and was not linked to other recent house fires in the Mornington area.
"It is unexplained, so the likelihood is someone is to blame for it ... but exactly how it started we don't know at this stage."
Southern Region Fire Safety Officer Barry Gibson said the fire was contained in a concrete unit on the first floor.
"The inside of the unit was extensively damaged by heat and smoke."
The fire had the potential to be dangerous as those living next door would have to walk past the unit to vacate the building.
There were no sprinklers or smoke alarms in the unit, and this was another reminder to install them, he said.
