Birdwatching is truly one of the cheapest possible hobbies you can have. Yes, you can make it expensive if you're committed to photographing them and traveling to remote locations to find "life list" birds, but that's not the vast majority of hobbyists.
Pretty much agree. Binoculars are essential though, unless you really just want to watch geese and herons and things. And for binoculars you do want to spend a few hundred dollars at least if you can. It really transforms things when you can start watching/identifying the small birds.
