In no particular order, this is what it takes:

* Acting or improvisation;
* Voice training (singing, voice over workshops, public speaking);
* Digital sound engineering (mic technique; sound editing, mixing and mastering);
* Marketing and sales training;
* Basic business management;
* Accounting;
* General computer skills;
* Communication skills;
* Research skills for some types of voice work, especially audio book narration;
* Grammar, writing, copy writing (basic grammar skills are important though a lot of copy breaks basic rules because people don’t generally speak using correct grammar; but you need to know the difference; although you may never write copy, having a sense of good copy helps with timing, punching key words and general delivery of the message).

Mastering your natural voice is important. Natural sells more than anything. These are just some basics.