It depends on how well the owner maintains the house. My dad spent some time nearly every weekend doing something around the house. He did nearly everything himself: painting interior and exterior, plumbing, appliance repair and installation, window frame adjustments. He even rolled out fiberglass installation in the attic, and in the process accidentally slipped off a joist and put his foot through the ceiling, but he fixed the drywall himself. About the only thing he didn't do himself was re-roof. I'm sure he saved a ton of money not paying contractors to do all that.

For someone who doesn't do upkeep, or can't afford competent contractors to do it, major repairs can happen any time, without warning.