Well clearly you should consider whether you have a talent for voice over. But let's suppose you have and move on from there…
I usually find that people's thoughts turn to equipment before anything else. So one's first thought could be about microphone selection, preamp, audio interface, or maybe even choice of DAW. But there are factors to consider that are much more important.
The first is silence. Voice over must be recorded in as near-silent conditions as possible. I've auditioned many self-recording voice over artists and I can tell you without a doubt that background noise is the absolute Number 1 problem.
Put it this way, if you can't record voice over with a silent background, you're never going to get any work.
But there is no such thing as complete silence, so how quiet is quiet enough?
Well one rule of thumb is that the acoustic background noise on a recording is quiet enough if you can't hear it at a listening level that is comfortable for speech. I'd add that if you raise the listening level by 6 dB and you still can't hear the background noise, then that should be quiet enough for most applications.
Low ambience level
The next factor is being able to achieve a low level of ambience. A typical living room is far too reverberant for voice over. So sound absorbing materials and structures need to be brought in to make the ambience really dry.
It doesn't take much imagination to realize that the smaller the room, the less absorbing materials will be necessary to lower the ambience level. So you might think that constructing a small booth will be the best solution. The problem here is that very small rooms tend to sound boxy, because their resonances are well up into the audible frequency range. So they are more difficult to deaden and achieve a pleasant sound.
There's probably an optimum size for a voice over booth in which it is most easily practical to achieve a very dry sound. You could look here for inspiration.
Control over popping and breath blasting
Microphones don't like some of the products of the human mouth. Speech and singing, yes. Bursts of air caused by 'p' and 'b' sounds and other blasts of moving air, then no. Popping and breath blasting are absolutely to be avoided for voice over.
The problem is that many people think that a little popping or blasting is OK. If you listen to the radio on your studio monitors or headphones you won't have long to wait to hear an example.
But it's not OK. If you can't record voice over without any pops or blasts at all, then someone else can. They'll get all the work and you will get none.
The answers to popping and blasting are 1. Use a mic that is designed for speech, like the Neumann BCM 104 or BCM 705. 2. Point the mic at the mouth but away from the direct line of fire of the breath. 3. If you still have a problem then use a mesh pop filter.
You might choose a more flavourful microphone, and yes, choice of microphone is significant. But if it is more prone to popping and blasting, you'll just have to take more care.
When you have a silent, dry studio acoustic, and are able to record without any popping or breath blasting at all, you're ready to get started on your voice over career. Just be prepared for a lot of competition…