It varies! It largely depends on how much existing influence you have and how much money you're willing to spend. An influential person like Darren Rowse, Neil Patel, or Seth Godin can start a new blog and be successful in weeks simply due to their influence. Any blogger with a sufficient budget can pay for the content, advertising, and marketing required to grow a blog into a top performer in a matter of months. For most small businesses, mid-sized businesses with small budgets, or newcomers to blogging, a blog generally takes around a year to start showing returns. The time it takes for your blog to grow can vary depending on how frequently you publish content, how well you perform topic research, and if you get lucky enough to earn any great backlinks right away, but that's a general estimate.