"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.