Do you feel like your 401k is at ground zero? You're not alone.

When it comes to direct investing in residential real estate and becoming a landlord, you should ask yourself: “What am I getting into?”

The equity markets have plummeted since the beginning of 2008, and investors have flocked to fixed income options in droves. Bonds are not flawless, so buyers should beware of the associated risks.

The rule of 72 is a good heuristic for estimating the doubling time of compound interest. Other rules are handy for estimating continuous compounding or the effects of inflation when your HP-12C isn't at hand.

If you are investing directly or through a bond fund, you'll need to know what types of bonds are out there. They include federal government-issued debt, bonds from government-sponsored enterprises, municipalities as well as corporations.

Before a bond or any fixed income security is bought by investors, the companies and securities usually pass through the arms of a bond rating agency. These agencies are charged with determining the risk inherent in a certain bond or issuer.

Most bond interest income is taxed at your ordinary income tax rate. But when you start to move into different types of bonds and accounts, you'll realize that bond income taxation is anything but standard.

If you are going to invest in bonds, you need to know what method is best for you. It takes a lot of money to build an individual bond portfolio so bond mutual funds and exchange-traded funds may be worth a look.

Just like any market or product, buying and selling bonds requires the understanding of key terms like coupon, yield to maturity, par and duration.

Bonds are a form of debt whereby investors loan money to a company, city or government. You can buy bonds directly from issuers or from other bondholders. There are also mutual funds which invest only in bonds.