I am consider making offer on a house that has a sump pump (the house
has no basement, just fairly small crawl space; there's a little
creek about 20-30 yards behind a house; also a lake about ¼ mile
away.)

I know nothing about sump pumps, so would appreciate any tips/advise.
Specifically:

1. What are the normal maintenance procedures; annual
operating/maintenance costs?
2. I'd be very afraid of the sump pump becoming an "owner
nightmare." What are the things that could go wrong? Worst case
scenario?
3. If, at some point, a new sump pump needs to be put it, how much
would that cost?
4. Could the fact that the house needs a sump pump be an indication of
bigger moisture-related problems e.g., mold?
5. Anything else I should be aware of?

The house is a ranch-style, 4 bedrooms, ca. 1,900 sq ft, located in
Littleton, CO (Denver metro), if that matters.

TIA