The CD is one of the most effective ways to create passive wealth over time and has been used by investors for generations. Ask your grandparents; it is highly likely they own CDs (TDs) with their local bank or Credit Union. This is done by creating CD ladders to maximize effectiveness. Most Bank and Credit Union CDs have zero fees attached unless you cash out before maturity.
If you’re looking for a way to begin gradually replacing your income, these are just some of the best ways you can do it as a physician. Remember the idea of gradual retirement? Passive income streams like the ones mentioned here are perfect ways to allow you to spend more time with family, enjoy your day job more, and, of course, make a little money while you’re at it.
What I Do: I’ve set up multiple investment accounts outside my main operations bank that deals with working capital e.g checking, paying bills. By transferring my money to a couple brokerage accounts and two other banks as soon as it hits my main bank I no longer have temptation to spend on frivolous things. As a result, I can wake up 10 years later and reap the rewards of compounding. My 401(k) is the best example where constant contributions over 18 years has grown to over $500,000 without any savings pain given it just became a part of life. Real estate is also a fantastic asset class for the long term. It’s fantastic to enjoy your home, pay down your mortgage each month, and end up with a paid off asset that has likely appreciated during your time of ownership. 
If you know anything well, a place, how to fix something, how to make something, how to do something, you can write a guide for it. You can sell your guide as an e-book, offer it as a download for a fee on your site or reach out to bloggers with similar content and ask if they will offer it as a paid download on their website (for a price of course).
In equity valuation, residual income represents an economic earnings stream and valuation method for estimating the intrinsic value of a company's common stock. The residual income valuation model values a company as the sum of book value and the present value of expected future residual income. Residual income attempts to measure economic profit, which is the profit remaining after the deduction of opportunity costs for all sources of capital.