Want to invest in “high-quality, attractively priced companies making a positive impact on the world”? Of course you do.

The question is, will you make money?

On Sept. 30, Thornburg Investment Management launched the Better World International Fund, self-described above. But if you have less than $2.5 million to invest, the fund will charge you an upfront "load" of up to 4.5 percent and an annual expense ratio of 1.83 percent. A no-load alternative version of the fund charges 2.38 percent of assets a year.

That’s just about how much non-U.S. stocks have earned annually over the past 20 years and 11 times as much as the fees on the most popular U.S. international mutual fund.

The new fund’s portfolio manager, Rolf Kelly, said investors will get something for the higher fees. “There is an additional layer of work and effort that’s going into this product,” he said, citing the costs of evaluating companies in emerging markets. “It’s up to us to prove our salt and earn our fees. It’s my job to justify my existence.”

Investors can expect to hear more and more sales pitches such as this one. Mainstream investment firms are rushing into “sustainable investing,” also known as SRI (socially responsible investing) and ESG (environment, social, and corporate governance). From 2012 to 2014, the number of U.S. investment funds incorporating ESG criteria jumped 28 percent, to 925, and their assets more than quadrupled, to $4.3 trillion, according to the Forum for Sustainable & Responsible Investment. Even the largest Wall Street firms are getting into the act. BlackRock, the biggest money manager in the world, started selling its BlackRock Impact U.S. Equity Fund on Oct. 13.

“The driver is client demand,” said Kathy Leonard, a 32-year veteran of sustainable investing who is a wealth advisor at UBS Financial Services in Boulder, Colo. “We need to have the products and services that our clients are asking for.”

Expect that demand to spike after an Oct. 22 ruling from the U.S. Department of Labor's Employee Benefits Security Administration. The ruling makes it clear that managers of pensions and 401(k)s should feel free to add ESG funds to their lineups. Previously, many avoided sustainable options for fear of violating complicated federal regulations governing retirement plans.

It’s never been easier to find an investment that promises to do good. It’s never been harder to sort through the jargon and marketing pitches to find a sustainable strategy that’s right for you.

Five Don'ts: Don’t Overpay

No matter how well-intended an investment strategy may be, it can’t avoid mathematical reality: Every dollar investors pay in fees subtracts from returns. But there are cheaper sustainable options, including index funds. The Calvert U.S. Large Cap Core Responsible Index Fund charges an expense ratio of 0.19 percent. The Vanguard FTSE Social Index Fund charges 0.27 percent.