There's no such thing as a proven business with guaranteed returns. There are legitimate ways to boost your income, but they are scarce, not always easy to find, and require a lot of hard work and commitment. I couldn't be more specific without knowing your skills, knowledge or ideas. You will no doubt come across numerous scams in your search for something suitable, those offering to show you how to make it big, with very little work involved, and all for a one off fee. If it sounds too good to be true, it usually is.