The work is lucrative, Ms. Tan said, and she isn’t planning to stop anytime soon.

“I was definitely not fully set up financially for retirement,” she said. Besides saving for her later years, Ms. Tan said, she is paying a mortgage and college tuition for a younger child.

Ms. Tan’s success is more the exception than the rule. Still, there are opportunities for older brand representatives because there are fewer creators in that age category to compete with, said Kevin Creusy, a co-chief executive of Upfluence, which manages a repository of 4.5 million social media creators that advertisers can comb to find partners. As of mid-April, the listing had only about 2,700 entries for people 60 or older, he said, and just 174 of those had a TikTok account. The group is also overwhelmingly female and white, he said, “an indicator that other groups may be underrepresented overall.”

Brands often look for creators with as few as 5,000 followers because those so-called nano-influencers are more likely to engage ‌with people in their comment sections, giving the account an authentic feel, Mr. Creusy said. Those accounts can also be an inexpensive marketing vehicle as creators sometimes feature a product just because they received a free sample. About half of partnerships formed on Upfluence offer free products as compensation, but no pay.

Creators who are paid can make anything from a few hundred dollars to tens of thousands to produce content advertising a brand. Pay rates depend on several factors: how much effort is involved in creating the post, how many times it will be posted and on which platforms, if the imagery can be used elsewhere by the company, and how many followers the creator has.