There is a huge market for this, and this option stands out from the rest as there is less competition in speaking voice in other languages than in English, so here you can fill a big hole in demand. Since there is no bureau to earn money in addition to your salary, you can subvert the companies that offer speech – which many companies will definitely be interested in, who will not save money?
However, you will need to have some proper equipment to offer some decent quality work – it is expected and required when there is money on the table. However, it does not require much more than using your current PC, downloading the free Audacity program and acquiring a fairly good microphone.
The new price of these microphones is from about $150 and up if it is going to be quality but count on at least $200. Ask in a forum where it’s about making videos, podcasts or amateur radio, so you’ll definitely get recommendations for what you should pay – for new hardware, but also get good prices for older but, good hardware.
You can offer introvert to podcasts, or advertise advertisements, and much more – only imagination sets limits, just make yourself visible in every way imaginable, thus earning money.