It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

How can you tell a good mutual fund from a bad one? It's pretty basic: if the fund is diversified, has low fees, and shows strong performance, it's a keeper. Of course, there's a wide range, but using the Zacks Mutual Fund Rank, we've found three mutual funds that would be great additions to any long-term investors' portfolios.

Let's take a look at some of our top-ranked mutual funds with the lowest fees.

Franklin Equity Income R (FREIX Quick QuoteFREIX - Free Report) : 1.04% expense ratio and 0.46% management fee. FREIX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. With annual returns of 10.8% over the last five years, this fund is a winner.

Third Avenue Value Fund Institutional (TAVFX): 1.14% expense ratio and 0.9% management fee. TAVFX is a Small Cap Value mutual fund, investing in small companies with stock market valuation less than $2 billion. TAVFX, with annual returns of 15.1% over the last five years, is a well-diversified fund with a long track record of success.

Nuveen Core Equity R6 (TIGRX): 0.4% expense ratio and 0.39% management fee. TIGRX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. With a five-year annual return of 12.19%, this fund is a well-diversified fund with a long track record of success.

There you have it. If your financial advisor had you put your money into any of our top-ranked funds, then they've got you covered. If not, you may need to talk.