During the pandemic, 2020, I saw several people who had a side hustle of seed starting and plant starts. One woman appeared to be a single mom who did very well with her starts. She seemed to be so very busy with people coming to get starts.
There is a man in my area who started smaller, and started a bunch of heirloom tomatoes. In a couple years he added all kinds of varieties of peppers. People drive a long ways to buy peppers from him. He has a large yard and now has a couple green houses that are of a good size. He is an artist and started doing this to be able to keep doing his art instead of other kinds of work.