Many people don't take voice acting serious. The misconception is that since the actor doesn't actually appear before the camera, voice acting isn't legitimate acting work. The truth is, acting with your voice can be more difficult than screen acting. With screen acting, you have the make-up and costumes to help get you into character. With voice acting, you have a script and a character description. You may have notes on how the character speaks, but it's up to you to create the voice and the personality that goes with it. If you're getting into voice acting, it will be much more than simply being able to make a variety of voices. You'll need to be able to tailor voices to specific characters and maintain that voice with consistency.
You will need to have an agent to get work as a voice actor. There are exceptions, of course, and it is possible to get work without an agent, but not likely. An agent won't guarantee you can make a living with your voice, but having one will increase your chances of getting regular work because the agents have the industry contacts. You can consult an online directory for voice talent agents and submission guidelines.
Getting into character when you do a voice audition is important. This means more than simply creating a character with your voice. Use your body. Create gestures to go with the character you're using your voice to create. This is something you should also take with you to a job as well. It doesn't matter that you won't be seen by an audience. Use the gestures and facial expressions to help you become the character.