The honest answer is you certainly could. There are those webmasters who are definitely earning thousands per month on Adsense. A misconception that newcomers to the business of building Adsense sites is that one Adsense site will bring in thousands per month. Those sites are few and far between. It can be done but it may be easier to go at it a completely different way.
Build more targeted sites instead of building one killer site that forces to you to compete with top Search Engines Optimizers. The art of building Adsense sites is that you can get them listed in the Search Engines for free if you pick the right Niche. The traffic that gets to your site from the Search Engines is free. You net revenue for these smaller niche sites will be much higher because you will not have an advertising expense. Your visitors will be highly targeted and more apt to click on your ads creating more revenue per visitor.
The niche is the selection of a particular topic with specific keywords that Adsense will pay a premium for when your visitors click on the Adsense Ads. A niche may not be the most trafficked site but it is a topic that people are definitely interested in and web master who advertise for those customers are paying a high premium to get the click. A less trafficked niche with less competition from other webmasters is easier to get top rankings in the Search Engines with a little effort. Picking a Niche with low traffic but high payouts means you are probably not going to make thousands for that site.
For instance I have a site that generates less than 600 unique visitors per month. When a visitor clicks on an Adsense Ad on this site I get close to $5 per click. That site can make anywhere from $25 to $150 per month with very little effort. I don't have to struggle for top search engines listings for this site because the competition is very low at this time. The people who search for this topic find my site in the Search Engines.
The visitors that come to my site via Search Engines are very zeroed in on the niche. I see 1 out of 3 clicking a link because they are truly looking for my niche. Picking a lowered trafficked high paying niche generates lots of clicks on Adsense ads, few visitors but high payouts when the visitors take action, $150 per month is not enough to quit your day job, but find 10 niches like this, update the sites a couple times per week. Multiply 10 times $150 and now you are bringing in $1150 per month. Add another 10 and you are up to $2300 per month. You can certainly find time to find new articles and new content for 20 - 50 sites if this is your full time job.
The moral don't go after the big fish when creating Adsense sites. Sometimes there is more money and less effort in the small Niches if you build them in Numbers.
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