No, there's no definite number of views in order for us to earn. Even you have only one view if that single viewer will click on your ads or buy from amazon or ebay you can earn. That's we are encourage to increase viewers from the search engines because they are the ones who are hungry for information and possibly click your ads for more to find what they are looking for.
The best thing to do is create hubs with good keywords that lots of people are desperate to read and have less competition.
Also don't be satisfied for one or two hubs create as many as you can, the more high quality hubs you write, the more money you can earn.