Actually, whoever snaps a pic holds the copyright. You can outright sell your copyright, or you can allow a company to manage your rights, or you can engage royalty free micro-stock companies to host your images and pay you a small fee for every time one of their subscription customers downloads one of your images.
I play with a microstock site and net .33 / image that somebody wants. The company gets a lot more of course. I ain't getting rich on that, but some folks earn a living that way. I pay for my ammo and a little gas money for pheasant hunting. I'm not serious about that because to be serious you have to actually work. Not working is what retirement is all about and every once in a while I send the company some pics and they tell me all the technical things that are wrong or they accept them.
This is my top seller - an old departed friend. Lots of different images of him do sell.
If anybody is interested in doing that with their own pics, send me a PM and I will be happy to guide you through it.
Cheers,
Jack