Those that are harness mounted or balance on a person's shoulder can be difficult or even hazardous to use in tight areas like an attic. On some systems lenses can be quickly changed. Beware of single element lenses. The price may be attractive, but the imagery is generally not good. Most imaging systems connect directly to a conventional portable video recorder, either VHS or 8 mm format.
Some systems are elegantly simple, while others are a jumble of cables and buttons.
This is great for permanent documentation. Some more expensive imaging systems are capable of storing the image on an on-board computer disc. This is a nice feature, but most of us will never need it. Several companies make such systems. They are definitely worth looking at, particularly if they will primary be used for auditor or crew training.