The biggest risk isn't a fire, it's someone hearing that he has a huge stash of cash in his house and robbing him. Are you familiar with Truman Capote's In Cold Blood?

You can play on his paranoia by pointing out (truthfully) that any nosy person who enters his house is liable to discover his stash and blab about it to God knows who. All it takes is one desperate person overhearing a rumor for him to have a really bad day.