A book used "realtor" lowercased, which prompted me to write the usual query about the National Association of Realtors. But the paragraph was taking place in 1830.
Ngram?
Yep, a short blip around 1830, not to appear again until the 20th century.
https://books.google.com/ngrams/graph?content=realtor%2C+real+estate+agent&year_start=1800&year_end=2022&corpus=en&smoothing=3