Typical advisor clients used to worked at places where they enrolled in a retirement plan on day one. Then, when they quit their jobs after saving money for many years, they never worked again.

But that model often no longer applies, with part-or full-time freelancers becoming a bigger part of the American workplace, and with "retirees" continuing to work past age 65.

It's a trend that advisors need to be aware of, as more clients in the coming years may be freelancers or independent contractors.

About 56.7 million Americans are independent workers, according to a study, "Freelancing in America 2018," that was co-authored by the Freelancers Union That is an increase of some 3.7 million over the past five years. Freelancers now comprise a little more than a third of the American workforce, the report said.

"Average weekly hours spent freelancing increased 72 million hours per week from week from 998 million in 2015 to more than one billion hours per week of freelancing this year," the report said.

The number of freelancers is expected to dramatically increase over the next two years, meaning financial advisors are more likely to be serving clients in this job category, the Freelancers Union added.

"We have freelancers even though we were not targeting them," said Robert Greenman, a CFP with his own firm in Portland, Ore. "They have special needs."

Advisors, Greenman said, can fill some of the roles of the traditional employer, who most employees have depended on for a range of services, including saving for retirement.

"Retirement planning is a big issue with freelancers and we need to help them set up plans." Greenman said. That means helping freelancers set up Roth IRAs and solo 401(k) plans, he added.

"In some ways, these plans can be simpler than traditional retirement plans because they are being set up for only one person and they can be run in a way in which there are low or no administrative costs," he said.

Another advisor said retirement is only one factor that makes independent workers a unique class of clients.

"Freelancers are a type of entrepreneur," said DeDe Jones, a CFP in Lakewood, Colo., "and as such need help around topics like tax planning, cash flow planning and business structure and record keeping."

Jones said advisors should help freelancers "create a strong foundation so our freelancers can take advantage of the benefits of being a business owner."

Jeffrey Fishman, an advisor and lawyer in Los Angeles, works with many such freelancers in the entertainment industry. He said they are often "creative types" with special needs.

"Freelancers can have erratic income. And that means freelancers often need help with cash-flow management and retirement planning, he said.

"While some self-employed professionals may have a basic IRA, they generally are not aware of other alternatives, such as the solo 401(k) or a SEP IRA," he added.

Fishman said independents often need tax help.

"They usually do not set aside any funds for taxes as nothing is withheld," he said, adding that advisors need to provide freelancers with tax education.

David Demming Sr., a CFP in Aurora, Ohio, said not all freelancers are alike.

"Some people keep full-time jobs and freelance," he said. "Others have retired from full-time work, but earn some money in the gig economy, which reduces how much money they need to take out of retirement assets."

Advisors, he said, should understand these freelance clients and why they are operating outside the traditional environment after they seemingly retired. They are often working in the gig economy at jobs that they never had before but dreamed of someday having.

"When you get paid for play, it is a wonderful thing," he said.