I can understand how you want to know a definite answer, but sadly, IM is no exact science, therefore - no exact answer.
Could be 10 could be 100 could be 1000 articles. It all depends on your niche, your audience, the products you promote, how good you areat pre-selling, how good was your keyword research and whether or not you can reach top 3 or first page at all on google. I know people who have done 10k/month with 30 articles and I know people who haven't made shit with 100+. I've also seen websites with 20 articles but only 1 of them brings all of the sales.
That said, it's all about trying and testing until you find what works for you... or doesn't. You might make it or you might not. You should look at this in terms of a long term goal, instead of quantifying everything. Strive for high quality, optimized content. High quality backlinks and just stay consistent. Your first sale might come after a year ( depending on your niche of course ) and you should be okay with that if you're playing the long game. What I found is that a lot of people give up too soon, which means that with consistency you might possibly just outwork your competition. This is a marathon, not a sprint.