Residual income is the best model for money generation. Once you master and build up one avenue, you can devote your time and money into another avenue. Eventually you start reaping the benefits of multiple residual income avenues. Enabling you to have complete financial and time freedom. I recommend to all people to build these types of asset models as they can greatly improve their life.
For those willing to take on the task of managing a property, real estate can be a powerful semi-passive income stream due to the combination of rental and principal value appreciation. But to generate passive income from real estate, you either have to rent out a room in your house, rent out your entire house and rent elsewhere (seems counterproductive), or buy a rental property. It’s important to realize that owning your primary residence means you are neutral the real estate market. Renting means you are short the real estate market, and only after buying two or more properties are you actually long real estate.
To save time and effort, a person can group two or more of their passive activities into one larger activity, provided they form an "appropriate economic unit." When a taxpayer does this, instead of having to provide material participation in multiple activities, they only have to provide it for the activity as a whole. In addition, if a person includes multiple activities into one group and has to dispose of one of those activities, they’ve only done away with part of a larger activity as opposed to all of a smaller one. 
Do you know of a successful business that needs capital for expansion? If so, you can become something of a small-time angel investor and provide that needed capital. But rather than offering a loan to a business owner, you instead take an equity position in the business. In this way, the business owner will handle the day-to-day operations, while you will act as a silent partner who also participates in the profits of the business.
Residual income is calculated as net income less a charge for the cost of capital. The charge is known as the equity charge and is calculated as the value of equity capital multiplied by the cost of equity or the required rate of return on equity. Given the opportunity cost of equity, a company can have positive net income but negative residual income.