And the World Economic Forum predicted in a January 2016 report that five million jobs will be lost by 2020 in the 15 largest economies.

In this environment, women are already paid less than men and having a tougher time climbing the corporate ladder, particularly to the executive suite.

They're also behind the eight ball when it comes to retirement savings; with lower salaries—an October 2016 Economic Policy Institute report found that women working full time make only 80 cents for every dollar a man makes—they have less money to save and thus receive less matching funds from employers on those lower contributions than men.

Nely Galan, former president of the Spanish-language network Telemundo, was cited in the report saying that women are more vulnerable than men to job instability, which makes it even more important for them to have a side hustle.

And she's not the only expert to believe that women—particularly older women—need to venture into side-hustle waters.

According to Lauren Stiller Rikleen, president of the Rikleen Institute for Strategic Leadership, older women are generally more vulnerable to losing their jobs and they have a harder time finding new ones.

In the report, Rikleen pointed to a 2015 study from the National Bureau of Economic Research that found older women get fewer callbacks on job applications than younger women, although the callback rate for middle-aged and younger men were about the same.

Rikleen's interviews with hundreds of women in their 50s and 60s revealed that many of the women were subjected to curtailed responsibilities and lower pay by supervisors, "even as they were supposed to be working their way up the corporate ladder."

She also believes women are disproportionately affected by ageism, gender bias and the focus on their appearance.

Rikleen was quoted in the report saying about such double standards in the workplace, "It's terrible. To say 'it's not fair' is an understatement."

And being downgraded on pay that's already not the equal of men's becomes dangerous as workers get closer to retirement; those lower salaries mean lower savings, giving women less of a retirement fund to draw on when they stop working.

Galan advised women to start small, if they must, even if it's only an hour a week selling items online. New platforms allow creativity in devising ways to make money and build a side business, and perhaps most important, it will teach them business practices. She said in the report, "You will learn business whether you like it or not. Not everyone is going to start a business, but everyone can exercise that entrepreneurial muscle."