The Cost of Upkeep

While that might sound like a reasonable length of time, the appliances in your home aren't necessarily going to be new when you move in, so you may end up replacing them a lot sooner.

Then there are the really big-ticket items. Heating, ventilation and air conditioning systems require regular maintenance in order to work efficiently, but even in the best-case scenarios, most components only last 15 to 25 years, according to the NAHB. The life expectancy of a roof varies widely by the type of material, with slate, copper and clay or concrete roofs lasting more than 50 years, while asphalt shingle roofs last for about 20 years and roofs made of fiber cement shingles last about 25 years.

"If you live in a house that's 100 years old, virtually everything has been replaced," says Frank Lesh of Home Sweet Home Inspection in Indian Head Park, Ill.

Lesh, who is also the president of the American Society for Home Inspectors, says he tells his clients they should budget 1% of the value of their home each year for maintenance. "If your house is worth half a million dollars, you're certainly not going to spend $5,000 on maintenance each year," he says. "But some years, if you need to replace the roof or the furnace, you'll certainly spend more than a few thousand dollars."