Many investors reach a point in their lives when growth isn't nearly as important as income. The reliability of that income is also paramount.

One great alternative is to invest in exchange-traded funds (ETFs). It's simpler than choosing individual stocks and bonds. Granted, you still must be smart about which ETFs you buy. You'll especially want to consider the funds' costs.

Vanguard enjoys widespread popularity because of its low costs and the variety of ETFs offered. Income investors can find several attractive funds, but three especially stand out right now. $100,000 spread equally across these Vanguard ETFs could pay you $5,400 in annual income.

The Vanguard Emerging Markets Government Bond ETF (NASDAQ: VWOB) currently offers a 30-day SEC yield (the fund's annualized income over a trailing 30-day period dividend by its assets) of 6.1%. Investing one-third of $100,000 in this ETF would provide an annual income of roughly $2,033 based on this yield.

This Vanguard ETF attempts to track the performance of the Bloomberg USD Emerging Markets Government RIC Capped Index. The index is passively managed and provides exposure to bonds primarily issued by governments in emerging markets.

The ETF and its underlying index often won't exactly align. For example, the Vanguard Emerging Markets Government Bond ETF currently owns 747 bonds with an average effective maturity of 12.1 years. By comparison, the Bloomberg Index includes 726 bonds with an average effective maturity of 12.2 years.

Vanguard launched this fund in May 2013. Although the ETF didn't perform very well during much of this period, it's been a different story over the last year with a gain of 19%. Costs haven't eaten into the fund's returns much, though. The Vanguard Emerging Markets Government Bond ETF's annual expense ratio is 0.2%, well below the average expense ratio of 0.99% for similar funds.

The Vanguard Long-Term Corporate Bond ETF (NASDAQ: VCLT) has a 30-day SEC yield of 5.28%. This translates to around $1,760 of annual income if you invested another one-third of your initial $100,000 in the fund.

As its name indicates, this Vanguard ETF focuses on corporate bonds with maturities well into the future. It owns 2,996 bonds with an average effective maturity of 22.5 years. These bonds are all investment grade but typically not with the highest credit rating: 43.5% have a credit rating of A (low level of default risk) and 45.3% have a credit rating of BBB (moderate level of default risk).