Things in history that are similar to long term employment:

1. Soldiers e.g. legionnaires in the Roman empires

2. Filial relationships e.g. a lord and the subjects of their court

3. Apprenticeship with a master

4. Membership in a guild that held a monopoly for services within a region

5. Servants and bonded laborers,

6. Monks and Priests

7. Artists, writers, musicians and scholars with wealthy patrons

8. Professors, teachers and tutors

9. Various artisans and craftspeople employed in a noble's household

...

There are not exactly the same as modern employment but they do have many of the same characteristics (long term relationships, valued labor, etc...).