What full time jobs can someone get in the field of ancestry work?
Librarian. Though you would have to learn other fields, there are people who go to libraries to try to look up their ancestry, and knowing what sources to look for would be a tremendous asset. Besides public libraries, there are librarians that specialize in government documents. You could also try working for a local historical society or organization. If there are any volunteer posts open, you might want to try for one.
There are professional genealogists. Not many of them work full-time. Ancestry.com has a "Hire a professional" option. Once in a while a rich person will die without heirs, and a law firm will hire a genealogist to find the deceased's 2nd cousins. If you live next to a major resource, like the FHL in Salt Lake or the state archives for your state, sometimes people will hire you to look things up for them, because it is cheaper than flying across the country, renting a hotel and eating in restaurants.
Very few! Archivist is one, but they always get thousands of applications for such jobs. You'd need a degree in some area of research/history/genealogy/archiving/document preservation and loads of experience.
pretty 'narrow' field ........................................................
can you tell me why my name is james please? i need to know my mom wont tell me