People who use AdSense on their site just don't earn much with one site only. They have a number of blogs that generate a good amount or revenue from AdSense when combined.
One person has 6 sites each earning 30 USD a day (so that total totals to 180 USD a day).
If you have two or more sites you could provide links between these site so as to increase link popularity.
Yeah, hosting and domain name may not be covered by your AdSense earnings the first few months. A tip there is to have a domain name (complete with hosting) and use the subdomains to focus on a certain theme or niche for your AdSense.
And to monitor which ads are clicked more you can use the AdSense channel feature.
Adsense recently has rules on not disclosing income from Adsense so there isn't much info products about Adsense. And made for Adsense website are banned.
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