One of the most important life decisions we make is the choice of a career. As Judaism is most concerned with so many of the minor decisions we make - how to farm, what to eat, what to wear - surely it has much to say about what will occupy many, perhaps most, of our waking hours. So it may appear somewhat surprising that we find next to nothing, neither in the Torah nor in the vast corpus of the Talmud about career choices.

Yet this makes perfect sense. The Torah has little interest in what we choose to do for a living. Different people have different interests, talents and abilities. Each should choose according to his or her personal situation and inclination. This is of little interest to the Torah. What does interest the Torah is that whatever we do choose,  we do with the highest level of ethics, holiness and morals. We must avoid misleading advertising, unfair competition, overpricing. We must ensure our workers are paid on time, are not treated as slaves and that we pay our taxes. Our work must be part of our avodat Hashem, our service to G-d. 
In addition to the important aspect of providing for our families, work should be dignified, ennobling, and a method of seeing G-d in all that we do.[1] The Torah does provide a model of how work can be integrated into our religious worldview through the laws relating to farming. The Torah details a series of mitzvot helping the farmer to see his work as implementing Torah in the real world. Laws that ensure the poor are cared for, the land is not overused, the farmer has time for study (and even travel), the animal and plant kingdom are given their separate domains and so on and so forth. It is our task to ensure that whatever the profession of our choice we too are able to advance the values of the Torah in our work.
It is not until we arrive at the 81st and last page of masechet kiddushin and end of seder nasim that we have our first teachings on what might be called career guidance[2]. And as we might have guessed the context for the discussion is a moral one. The Gemara has been discussing the laws of yichud, the prohibition of unmarried people of the opposite sex being alone together. It is in this context the Mishna (Kiddushin 82a) teaches that a single man or single woman should not become teachers[3]. The Gemara explains that we are concerned that the teacher may have an affair with a parent of one of the students. While this may have seemed far-fetched, with what we have learned in the past generation such a fear cannot be dismissed so easily. 
This explanation is actually the second the Gemara gives. It initially suggested that the Mishna was afraid that a teacher who is single might molest his students. The Gemara rejects this explanation by noting that molestation is not something we need to suspect happening, something which no longer can be said with any degree of certainty. What we can say with certainty is such a fear is warranted even with those who are married and that while rare when it occurs the results are devastating and tragic. 
From this localized discussion the Mishna broadens the discussion to one regarding career choice in general. There are those careers which make religious life easier and those more difficult. In Mishnaic times professions best avoided if possible included a shopkeeper, a donkey driver or a shepherd as they provided easy opportunity to cheat. In a beautiful comment Rav Yehuda notes that "donkey drivers are mostly wicked, camel drivers are mostly good and sailors are mostly pious". The former often overcharge but as camel drivers spend much time in the desert, a place where survival is not easy they tend to pray a lot and be on good religious behaviour. And with many a ship sinking sailors were in constant fear causing most to be super honest in the hope that G-d would protect them. There really are no atheists in the foxhole. 
Rav Yehuda goes on to note that "tov sheberofim legehemon, the best of doctors to hell." To say that such is difficult to understand would be a great understatement. There is no greater mitzva than healing people and pikuach nefesh overrides almost every mitzva. It is not by chance that some of the greatest rabbis in history were also physicians, thereby providing both physical and spiritual leadership. It is precisely because being a doctor is so potentially great that the practice of medicine can be of great harm. As Rashi notes doctors run the risk of arrogance, forgetting that they are only messengers of G-d who is the One to ultimately decide who shall be healed and who not. Arrogance leads to mistakes which in a medical context easily translates into "killing people." In addition there are those doctors, Rashi notes, who will not treat those who cannot pay causing untold harm or even death to the poor. 
The Mishna advises we pick a profession that is "kav venaki, clean and pure, and pray to the One to whom riches and property are His, for there is no profession that does not have those who are poor and those who are wealthy, because poverty is not because of [our choice] of profession and wealth is not because of [our choice] of profession, rather all is according to one's merit." (Kiddushin 82a)
There are wealthy barbers and poor doctors, successful entrepreneurs and businesses that fail. And more often than not it is events beyond our control that determine much of our success. The price of oil, a natural disaster, new political leadership, currency fluctuations, the list of what contributes to our successes or failures is endless. Our education, business savvy and experience can only go so far. 
Our true success is measured not in how much we make but in who we are. Let us choose a profession that brings out the best in us[4]
[1] It seems to me that one of the reasons we are all too familiar with Jews who follow the rituals of Judaism but whose business practices are wanting is because work is viewed solely as instrumental to making money. It is all too often divorced from our spiritual lives and seen as something we must do but not as a religious endeavour. There is much to say on this issue one we will encounter with greater frequency as we soon begin Seder Nezikin. 
[2] In my home province of Ontario one of the requirements for graduation is a half year course in "careers". 
[3] As we all know this law is observed more in the breach. For possible justification of this practice see Rav Moshe Feinstein Igrot Moshe, Yoreh Deah 3:78.
[4] Even as I write these words I am most cognizant of the fact that as we are forbidden to rely on miracles many, nay most, choices of profession are not feasible for any person who has children in the day school system. This is a side tragedy of the tuition crisis and another reminder how Torah in its totality can be practiced only in Israel.