One of the biggest perks to closed-end funds is that they offer an income stream that can be a valuable part of your investment portfolio.

"There's a whole lot of factors that go into the analysis of the appropriateness of a closed-end fund within an asset class. But income is really a critical and an essential characteristic," says Bill Meyers of Nuveen.

Although not as highly publicized or as well known as ETFs, closed-end funds have long been valued by advisors and investors as a tool for potentially boosting investment income.

With market yield still low and volatility returning this year, now maybe a particularly opportune time to consider adding closed-end funds to your portfolio and your clients' portfolios.

Want to Buy $1 Worth of Stock for 90 Cents or Less? You can with certain so-called "closed-end" mutual funds - an often overlooked investment class. Click here to register for a free online video in which TheStreet's retirement expert Robert Powell and an all-star panel tell you all you need to know. The webinar is sponsored by Nuveen.