People that never actually built content sites think it's easy. People that never purchased domains for resale, think it's easy.
You can build a content site now about any niche and hire the best article writers, the best designers, and update once every hour and after a year have nothing but a lot of contact form and comment spam attempts to show for it.
Without real authentic backlinks to your content you are not ranking for anything that has search volume and the chances of getting people linking to your site (not the fake spam backlink packages) is almost 0. There is a reason domains with big quality backlinks go for a lot of money, if it was easy to get this any other way, those domains wouldn't go for 10k plus.
What about getting visitors to return on their own? Your guide about building content sites misses that. Should you use push notifications for new content and ask users to agree? Should you collect emails? If you don't plan correct, one change in Googles search algorithm and if you did manage to make some monthly income, it can go to 0.
Using math to make a case is flawed. Everyone does it. If you do day trading and have a small account of 5k, if you just try to earn 1% a day, for example, if you find a stock that is trading at 1 dollar and you buy 5000 shares, if it goes up just 1 penny you made your 1%, how hard could that be? You might be able to do this a few times a day too on some days, in a year if you keep reinvesting the with the profits, you will turn that 5k into 188k, even if you just count trading days and take days off you can cut that in half and still have turned the 5k into about 90k. Now imagine if you find a stock that moves just 5 cents up, after a year your 5k will be $280 Billion, you'll be the richest man in the world! Check the match
https://www.thecalculatorsite.com/finance/calculators/compoundinterestcalculator.php
In the 90's there was a guy on TV selling a course that showed you how to make money with classified ads. He said if you find a product that sells in classified ads and you make just 10 dollars profit a week from it, you can just replicate it and place that ad in 3000 news papers and now you are making 30k a week. People fell for it.