You can also use keyword research to find out what people are looking for and choose categories from your findings. Unless you find someone who sells their private label rights material at a cheap price, most of the article batches will be priced higher than they would if they were in a membership site. You have to pay for convenience.

Even with that, the articles should be of good quality. You can subtlety advertise on different forums and pay per click (PPC) websites, such as Google. People are not going to always have time to create their own articles, so purchasing private label articles from you would be profitable for your bank account, especially if your articles are of good quality.