You make a pretty big assumption here: that anything you can invest in to earn money passively CAN be guaranteed. What you mean by "generate guaranteed income" is "to allow me to grow my investment". After all, investing $100k in a house that loses 10% of its value is worse than just keeping the $100k in dollar bills. In fact, if it is still worth $100k nominal down the line means you lost 2-3% per year on your investment. So after mortgage, property tax, maintenance, and everything else, your renters would have to cover about 7-9% of your home's value every year for you to make a 2-3% margin.

What I've found is that the reward is always proportional to the risk--otherwise people invest in it until it isn't proportional anymore.

Please investigate this for yourself, but personally, I take a two-way split-risk strategy to grow my investments:

- Very high risk, very high reward investments that I thoroughly research and believe extremely strongly in, using money I can afford to entirely lose.

- Very conservative investments in indexing ETFs that have rock-bottom annual fees and decent dividends.

Here's an article you might find interesting:

http://www.npr.org/2013/06/05/188306471/resisting-the-tempta...

In order of risk:

- Online savings @ 0.80% (Risk is loss of purchase power)

- I-Bonds @ 1.18% (Risk is loss of purchase power)

- CDs @ 2% (Risk is early withdrawal penalty + lock-in)

- Bonds @ 3% (Risk is drop in value)

- Stocks @ 4%+ (Risk is drop in value)