This is mostly for those who do not speak English as a first language, or those who wish to improve their grammar skills beyond the norm...would you invest in grammar lessons or information products?

This is a question I ask because I'm considering producing workbooks geared towards those wanting to improve their grammar. While my main target is freelance writers wanting to make more money, I also want to target the general public.

Please let me know what you think about this idea. Honestly.