Affiliate marketing is the practice of partnering with a company (becoming their affiliate) to receive a commission on a product. This method of generating income works the best for those with blogs and websites. Even then, it takes a long time to build up before it becomes passive. If you want to get started with affiliate marketing check out this great list of affiliate marketing programs.
If you have 20 years left to live and only require $60,000 a year, having $1,200,000 can also be considered enough even if you make zero return. The only problem is that your purchasing power will decline by ~2% a year due to inflation. The other problem is that you don’t know exactly how many years you have left to live. Therefore, it’s always better to have more rather than less.