Here is a video that demonstrates the importance of controlling exterior water and the importance of a sump pump if a home has a basement. Without this sump pump the basement would have flooded. With this risk it would be a good idea to have a backup sump pump system.
This is a back up system I recommend for homes with city water.
Basepump HB1000 Water Powered Backup Sump Pump
Ohio Home Inspection Videos 
Sump pumps can be a hazard when inspecting. Not fun when they are not properly installed.
pumps are necessary tools of each family, so to choose a good pump before buying should view the detailed assessment of the pump that was used previously : http://sumppumpspro.com/