Yeah, there are different language/location requirements for different content mills. Textbroker has different sites for different locations but many are more international and judge only on your written ability. Again, it depends on the mill. Textbroker for example has a lot of flexibility due to its rating system, it's very easy to get in at 2* and I imagine many here would be rated at 3*. Four stars a harder as it requires a more thorough understanding of grammar that isn't generally developed naturally (IE native speakers). Keep in mind with your comment regarding native speakers, most don't actually take any further education in their native language beyond what's compulsory. They often make little grammatical errors that will immediately stand out to an editor, even if they sound very natural and otherwise communicate well. It's not that uncommon for foreign learners to overtake them on strict adherence to the rules. I know of someone who moved to Germany and joined the German Textbroker as a way to improve their writing. They were initially graded at 2* but slowly climbed up and ended up earning a nice income on the side, in addition to becoming proficient in written German. Due to Google recently upgrading its algorithms 2* level articles are a bit less desirable than they used to be, though.