I would never recommend this to anyone.The good thingsYou control your time, so that's good. About 50% of the students are quite fun to teach, so you'll be less stressed than normal jobs. But that's it.
The challengesThe company and management itself is not considerate of their online teachers. They keep adding up rules and features that would inconvenience the lives of the teachers. They'll always be hiring not because they're getting more and more students (actually, there was an ordinance or law in the other country where they don't encourage classes outside regular school anymore), but because only a small percentage of the teachers would actually last for a long time. So as of now, I can say that if you've been a teacher in 51Talk for a long time, then it's tolerable but if you're just starting...well, I bid you good luck.