I have a Nikon D7000 with 18-105mm lens. What kind of rain cover is available for my camera? What are the advantages and disadvantages of different types?
I know seasoned professionals who use pro level gear in light rain without any cover. If they need to cover up due to a heavy downpour or other environmental factors (such as a Color Run or Holi Festival), they often use a clear trash bag and rubber bands or gaffers tape to create a cover for their gear.
There are products specifically created to protect cameras and lenses from the environment while they are being used.
Plastic rain covers are made of clear plastic that is a little thicker than the typical trash bag and are shaped to fit a camera with appropriate openings for the lens and viewfinder. They usually have a drawstring to pull the cover tight at the front of the lens and many have a small hole designed to fit over the viewfinder that is held in place by the camera's detachable plastic/rubber eye cup. They are available in multiple sizes to accommodate different lens sizes, and some even allow an hot shoe mounted flash. This two pack sells for $6.99 in the U.S. at amazon.com. This one has hand holes on each side and room for a flash. You can spend considerably more for a cover with more features if you are so inclined. This bag can be stored around the lens hood when not in use and deployed quickly when the weather dictates. It is also more durable than the cheaper bags which are normally only good for a few uses before they need to be replaced. If your lens is not weather sealed, you should probably use a screw on protective filter as well.
Products made for underwater use will also protect your camera from weather and other environmental factors. They will do so at a higher level than most plastic rain covers, but you usually give up some functionality in exchange. You may not have access to all of the control buttons and knobs when your camera is in a dive housing. The lower end dive housings are also flexible bags with various shapes for different camera/lens combinations, but unlike the rain covers they seal up. This one sells for about $70 USD. A customized hard case dive housing will probably cost more than your camera, but usually allows better access to your camera's controls and offers a greater degree of protection. This one is customized for the D7000 and requires an additional lens port for each lens you wish to use.