Brand-new houses are subjected to countless checks before you move in -- by architects who draw the plans, building inspectors who keep track of construction and bank officers who make the loans, to name a few.

Older homes are more like used cars: spiffed up on the surface and full of surprises underneath. Some major components, such as septic systems, can pose problems that are difficult to spot -- and they may not be evaluated in a written, home-inspection report.

Typical systems have a holding tank that collects solids and needs periodic pumping, and a drain field -- an underground network of perforated pipes in a gravel field designed to gradually drain liquid waste back into the soil.