The Rebbe's guidance on choosing a profession, taking a job, and changing jobs:
Choose work that is stable and meaningful. Temporary work can help, but seek a stable livelihood (IK 724). Choosing work that benefits others, and using one's talents for the good of Klal Yisrael, brings blessing (IK 5505, 10050). Where basic needs are covered, work that brings long-term fulfillment is ideal (IK 3344). When circumstances are uncertain, prefer a path with a shorter preparation time that allows earlier progress (IK 10153).
Every profession can serve Hashem. Each profession contains lessons in serving Hashem, and can be a platform for spreading Yiddishkeit (IK 505, 7885, 9585). Be especially G-d-fearing in one's work (IK 861). A person's mission may include both a profession and supporting Torah (IK 8200).
Accepting a job offer: clarify the financial terms and job security first (IK 9406). Accept only with rabbinic approval where relevant, without dispute with others, on proper terms, and with one's spouse's agreement (IK 10265). A permanent offer that comes one's way can be a sign of Divine providence to proceed with confidence (IK 6679). For a young man, a realistic full-time position is generally preferable to kollel unless he feels a specific calling to learn (IK 9971).
Leaving or changing a position: don't leave a position lightly, especially one in holy work or rabbinic service; additional income alongside it is fine (IK 2859, 9235). Such decisions need deep reflection and the counsel of impartial advisors and trusted mentors, and patience before making changes on one's own (IK 5723, 9865, 10021, 10965).
Vocational training for youth: learning a trade is positive, but not at the expense of Torah study at the key ages; for a boy struggling in yeshiva, vocational schooling together with Torah study, close to home, can be the right path (IK 3556, 4489, 9152). Vocational programs should be kept separate from the main yeshiva (IK 1297, 1533).
See also: פרנסה – תורה ופרנסה.