on Jane Friedman site:

Anna Sewell sold her only novel, the classic Black Beauty, when she was 57 years old. She had worked on it for six years while confined to her bed due to ill-health. It wasn’t until after Laura Ingalls Wilder had celebrated her 65th birthday that the Little House series came to prominence. And teacher-turned-memoirist, Frank McCourt, won the Pulitzer Prize for his book, Angela’s Ashes, at the age of 66.

When my debut novel, Lies That Blind, came out on October 19, I was two weeks short of my 67th birthday. Becoming a novelist has nothing to do with your age. Nor should you think that having invested your talent so far in one literary arena—as I did with nonfiction—that it’s impossible to shift gears. I’m proof positive you can do both.