Subtitle business idea for online courses and tutorial videos recorded by non-native English speakers. Specially other non-native users looking for these training videos, have problem understanding professional content that are pronounced with accent.
You can sell these subtitle files on an online shop as a digital files eCommerce business, or even work directly with video creators.
To expand it, you can do it for other languages other than English. Like Arabic subtitle for a programming language training video recorded by an Indian pro coder.