While having a broad set of voice skills is beneficial, many voice overs establish themselves in commercials and more general corporate voiceover work before specialising. Having a niche or specialist focus though can make a difference in earning potential. So, bearing in mind the question: how much money do a voice actors make, will also depend on the level and experience in a given niche e.g. animation, audiobooks or gaming.
Like pacing, vocal tone and inflection refer to ensuring you speak in a natural and pleasant manner. You want to be friendly and engaging, but not so much that you sound fake. No one wants to sound like a game show host. But, you also want to avoid monotone robot voice which, like pacing that’s too slow, can be boring and off-putting for listeners.

Your own voice is your most important piece of equipment. If you're new to the voice-acting world, look around to see if there are classes or coaching in your area. Outside of class, practice speaking clearly and confidently. Learn to do this even with material you've never seen before. It's also important to learn voice care – straining or injuring your voice can hurt you and your career.
As editor, you need to turn the raw recording into the final version of the file you'll be sending to your client. Editing during a recording session can be problematic, and particularly so if you're recording in a domestic environment. How can you expect to hear the drone of the dishwasher ruining your recording if the dishwasher is still running as you edit? I'll look in more detail at setting up a voiceover recording studio next time, but for now, if recording in a separate room or isolated booth isn't an option, at least try to edit the file the following morning (or maybe at night) when there's less noise around — because hearing your recording with a fresh ear and in a quieter environment will help you to make better editing decisions, and will reveal noises that slipped your attention earlier.