Increase your payout with subdomains

If you have more than one topic you would like to blog about, dont just blog it on one place. Search engines will compare the significance of each post with the other. So if you have a entire blog filled with one topic your blog will go up higher for that topic. That''s why if you have more than one topic to write about, why not start a subdomain and another blog on there which doubles your income, as well as makes your subdomains and you blog higher up in search engines which in return gives you more visitors.