How long do you have to go to college to be a photographer?

To build on what Pran said, there are benefits to a photography degree. You'll get your work critiqued by professionals, you'll be given opportunities and access to equipment and locations that will help you develop your skills, and you may learn things about composition and the finer points of what makes a good photograph that you may not have known before.

But it'll cost you tuition, books, time, etc and in the end, you'll likely be photographing weddings. Photography is one of those things where someone with natural talent and some decent equipment can be great, even without formal education.

However, photography, especially at the higher levels, like nature, fashion, etc can involve some complex technology, tricky lighting situations, etc. A formal education in photography is not necessarily a waste of time, if you are deeply committed to and interested in the subject.

Technically you don't. My brother got a bachelor's degree in mechanical engineering, but decided he'd prefer to be a wedding photographer. He never went to college for that, just started a business and slowly ramped that up as he ramped down on his engineering job. Your portfolio and contacts are very important for something like that, because it's all about getting clients.

That said, his experience probably is not typical, so take this with a grain of salt.

And building on what Ethan said, on the higher end of photography, which is shooting for advertising and corporate clients, a college degree comes in handy for reasons you wouldn't necessarily think of. A liberal arts education helps you understand psychology, history, art history, communications, business, marketing, writing, etc - all of which help you understand what a photographer does: capture a still image which evokes emotions and desires. You don't necessarily have to be "educated" to be good at this, but there is an ocean of talented photographers who can't make a living because they can't understand the message behind the photograph, can't convince a client that they can do the job, or can't effectively run a business. College helps with all that.
Good luck!