1. One should not sell haraam products e.g. pork, carrion, wine, etc.
2. One should exercise moderation in earning a livelihood. So much of time should not be given to the business that one begins to neglect the rights that he owes to Allah Ta’ala and the rights he owes to his wife and children.
عن جابر بن عبد الله، قال: قال رسول الله صلى الله عليه وسلم: أيها الناس اتقوا الله وأجملوا في الطلب، فإن نفسا لن تموت حتى تستوفي رزقها وإن أبطأ عنها، فاتقوا الله وأجملوا في الطلب، خذوا ما حل، ودعوا ما حرم (سنن ابن ماجة رقم 2144)
Hazrat Jaabir (radhiyallahu ‘anhu) reports that Rasulullah (sallallahu ‘alaihi wasallam) said: “O people, fear Allah Ta‘ala and adopt a good effort without exerting yourself in searching for sustenance, for certainly a person will never pass away until he receives his full share of sustenance, even though it may take a while in coming to him. Therefore fear Allah Ta‘ala, and adopt a good effort without exerting yourself in searching for sustenance. Acquire halaal wealth, and refrain from haraam.”