1
general::
Begin, as in He started in serving, without taking any practice. [Late 1800s] Also see START OUT.
American Heritage Idioms
2
general::
Phrase(s): start someone in (as something) [and] start someone out (as something)
to start someone on a job as a certain kind of worker. • I got a job in a restaurant today. They started me in as a dishwasher. • I now work for the telephone company. They started me out as a local operator.
McGrawhill's American Idioms And Phrasal Verbs