The best way is to make money online is also the best way to make money offline.
Educate yourself, thoroughly research the alternatives, seek objective advice from others once you've narrowed down the search, develop a realistic plan for your endeavor, then work as hard as you can to make it succeed. If you are planning to make the equivalent of the salary from a full time job by running your own business full time, expect to work about 60-70 hours per week for 3-5 years while you build your business. Then you will be able to back off to 40-60 hours per week.
Expect to lose money for at least 1-2 years and make sure you have to cash to support this. Assume you will have no customers for the first year. Pay attention to the lessons of numerous successful businesses - focus on effective marketing and make customer satisfaction your highest priority even if it means losing some money. When you are new one unsatisfied customer can ruin your business. Even if you have a warehouse full of gold bars and the best plan in the world, never forget that every customer is your most important asset.
Don't take this advice as critical or negative. It is reality. You can succeed if you go into a venture with realistic expectations and work hard.
Good luck.