Depends what you consider a good income. Without a doubt the easiest way of making money online is using sites like Fiverr to provide services, however that is trading time for money so there are limits on what you can earn, but $50 - $75 a day isn't hard to achieve. For many people that would represent a good income, particularly if it only takes a couple of hours a day.
Building an online business requires that a product is sold, so find an offer that converts, drive traffic to it, capture the leads, develop your relationship with your list of leads and rinse and repeat. Could be a product that you are an affiliate for or could be your own product. Just make sure it is high quality.