Content mills are more difficult than I originally thought

So I have joined a number of content mill locations (This is where you write a quick 300-500 article about whatever and they pay you for that article.). Some I think will work well, others I am worried about. For example, some places require you to earn X amount before you cash out – but have very little work to be had. Places like this will not work.

I think that these content mills will replace Amazon Turk; but they can not be the main source of income. Or rather, I think I will continue to look for new locations to sell content too. The idea is that hopefully I can build this pool of potential income.