If your basement already has a sump pump that was installed by the builder, chances are you are in a good position to finish off your basement. However, If you have a sump pump that runs often, you should consider adding a backup. There are two types of backups available. H20 and battery powered sump pumps are similar in price. Even though the water powered backup used a lot of water (when in use) it is a much better system that will not require any maintenance unlike the battery powered backup.
A sump pump should be tied to a drain tile that goes throughout the entire basement floor.