You can decide to go entirely on your own and e-publish. But you need to understand that it's risky. Yeah, there's not the kind of up-front costs involved in "real" books, but if you're not professionally edited, if you don't find someone to design a good cover, and so on, you're risking being lost in the wilderness.
I was at a writer's conference in April (Pike's Peak Writers Conference) and more than one agent and editor said that if you chose to e-publish, good for you, but if you now hoped to get a regular agent or editor, you needed to understand the stakes. You'd need to demonstrate very strong sales (they gave specific numbers at specific price points -- the lower the price the vastly greater the sales needed to be) to hope to get a mainstream editor or publisher in the future.
Personally, I'm enough of a newbie, and idealistic enough that I'm going to hold out for print. I do plan to attend that conference next year, and I plan to have at least one project completed so that I can pitch it to an editor or agent.