There are dozens of markets that employ content writers. This is not a definitive list but here are seven of the most popular:

Marketing 

• Social media (Facebook, instagram, Linkedin, etc.)

• Digital advertising (PPC, display, retargeting, native)

• B2B sales (lead gen, outreach, closing techniques)

• Content marketing (Blogs, YouTube, podcasts)

• Email marketing (conversion, deliverability, automation)

Personal finance 

• Mortgages

• Credit cards

• Taxes

• Insurance

• Banking

• Budgeting

Health conditions

• Diabetes

• Back pain

• Dementia

• High blood pressure

• Crohn’s disease

• Irritable bowel syndrome

• Asthma

Aging

• Products and services targeted at boomers

• Specialty travel

• Brain health supplements

• Cosmetics

• Part-time income

Individual professions

• Trade journals

• Blogs

• Podcasts

• Industry newsletters 

Ghost writing

• Books (for print)

• Ebooks

• Blog posts

• Speeches

B2B Products (Especially Software)

• Blog posts

• White papers