Rusty door hinge bolts?
 

Howdy folks. Looking to jump in and purchase, I've checked out several H2 08's and 09's, with mileage in the 40-60k range, and noticed they all have rust on the driver and front passenger door hinge bolts where the hinge is attached to the car body. Some are faint while some are horribly rusted, and it doesn't necessarily correspond to the degree of surface rust on the undercarriage.

Is this normal? What causes this and what could I do to fix it, or at least keep it from getting worse?

Any thoughts appreciated.