Being a Voiceover Artist is a lot more than just reading out your script out loud into any old microphone.
Almost all successful voiceover artists are current or former actors or broadcasters, building on the skills that they have acquired over previous years.Get your lips round that
You will need to know the proper way to speak into a microphone, be able to speak well, pronounce clearly with out irritating mouth noises, be able to take direction and enunciate properly. You may even be required to act. All these take years to perfect.You will need to know how to interpret and pace a script properly, as well as "lift" the words off the page and project your voice without sounding like you are shouting.
You can practise all you like but you will probably need some training and certainly a dash of innate ability to make money as a voiceover artist.