One of the most important rules is to ensure you value yourself as a professional. If you undervalue your own service it can be hard to later charge for the correct rates. A professional voice-over should cost a minimum amount, even if you’re new. If you allow clients to low-ball your work from the outset it will continue to set the expectation that they can get a voiceover from you on the cheap. This can then mean the difference between making a living and paying bills or not.
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.