Having a blog pays when it produces online traffic; having frequent visitors to the site. Whenever your website that's a blog receives a visit its producing online traffic in turn it attracts advertisers to book space on your site to market their product. Their several methods to close a deal with the online advertisers to your site about methods of advertisement to pay,to mention a few which could be: 1-advertisers paying you for the advertisement space 2- advertisers paying you per the number of clicks of their link to your site 3- advertisers paying on commission of sales... The list is long, but to begin your blog has to fulfil some requirements which are potential essential to attract advertisers and to get better deals. Your blog has to reach a certain threshold of frequent visits per month, for instance Google Add Sense considers blogs that have visits from 10,000 onwards per month to advertise on. And apart from building online traffic the topics of discussion play a vital role on determining the type of advertisements to anticipate. The blogs should also be of your legit work and not copy + paste, it can lead to legal infringement. Im in the path of building my own blog, but having success from earning well in blogging boils down to content, it should be your original work, and blogging on a regular pattern I.e twice every week, every Monday, Tuesday, Friday of the week... a regular pattern keeps your readers/subscribers on the loop in your trends, it grows your reputation as well. Once you begin blogging you can grow your channel through affiliate marketing; having your blog link posted on your competitors website, that way you will be directing traffic too to your website, though at a fee. Another way to earn from a blog apart from advertisers is through selling of digital media content such as ebooks, audio files, video files... Their endless possibilities to earning online, but it all boils down to producing content. You can inquire more I can assist you where possible, or need for clarification.