Such an occupation is a wrong occupation. Someone says that he does not kill any animal. But he rears cattle, sheep and goats, feeds them well so that they are fattened and sells them to the butcher. A certain person says that he does not take any intoxicant but sells intoxicants, alcohol, and other drugs like opium and marijuana. Whoever takes it from him breaks his sila .
Someone sells poison and makes a living.
Whoever purchases it kills someone with it. So one should examine oneself to see if one's livelihood is encouraging people to break the precepts. If that is so, that occupation is not the right occupation at all. Even in the highest profession, it is very important to know the volition of the person who is engaged in it. If his mental volition is not good, however good the occupation may be, it will not be the right one if it is not accompanied by a good volition.