So if I understand correctly, you want to get a free tool, that you can charge people to use? Bold.
There are javascript based html editors that can be used through a browser. they generally create ugly-ish code, but get the job done (my dad uses one for his work, and if he can do it, anyone can). Basically, it looks similar to the BBcode editing options above this text space as I'm typing this response.
other than that, I don't think you'll find anything free. Hosting companies have those sorts of things, but they're paying for them.