Bilingual could allow you to work in some capacity. But in teaching those people really don't always know why. Why is something correct or why is something wrong. What is probably a good learning path. Just think of average native speaker. They can tell that something is wrong, but they can't always explaining in common framework why is it wrong.

And then if you get money involved, you probably want version in both languages or even more. And those have to be correct exactly.