Create your web site, upload documents, earn popularity, connect advertising and better not only translate documents, and do your homework, which does not replace the documentation, lessons can be sold, this is serious.
And investors also need to look for it is in this vein, any such project requires large investments, need to make enough lessons to make sense to start advertising and selling, but it can bring good passive income with minimum risk.
when is the best time to do it?
Depends on the engine and your product may never, if at all unprofitable project.