If you are outsourcing articles, it is totally about trust and long term relationships. if the person that is writing your articles for you thinks they have more work coming from you, they aren't going to be selling the content to someone else. It partly depends on how much you are paying, and how unique your niche is. If you are buying in the "make money online" niche, and paying low dollar, it's going to be real hard to get 100 articles that look unique to begin with, much less arent very nearly what is sold to someone else. The higher you pay, the less likely the person is to use the content (or a substantial portion of the content) for another client. Personally, I write most of my own articles, because by the time I do the research needed to provide the information needed to insure I get unique articles, I may as well write them myself. Once you are experienced, it is possible to knock out quality articles of 400-500 words in 20 minutes, and 700 words in about 30 minutes each. For outsourced articles, I found I was spending 10-15 minutes per article (average). You may find you have a different ratio of time, depending on the niche you are promoting and how picky you are.