Ezine articles are terrific... Just follow their TOS. You are limited by the number of articles you can pull a year. If you want to go over the set amount, contact each author and ask permission.
I like to stick by the old motto "You get what you pay for". You say you want high quality, can free articles really produce high quality. Sure you might run across a high quality article on ezinearticles. At the same time, you might wind up with something that leaves the quality out. I just feel that your better off writing yourself or hiring a writer to write for you.
Well it is the same problem everywhere. The number of non english people here have problems with spelling and grammar. The reason that most of us English natives are making money writing on here.