People think that going for professional jobs is better than doing vedic rituals.It is not so!.The shastras order brahmins to make their livelihood only by their swadharma i.e.,
1)Adhyaapana (Teaching vedas& shastras)
2)Yaajana (officiating other people rituals like soma yaga,agnihotra..)&
3)Prathigraha. (Receiving gifts).
Earning by other means other than the above three ways is not destined for brahmins.If survival is difficult during emergency periods the shastras has allowed some occupations during such situations.But still it would be considered great if he sticks to swadharma (ie.,above 3 ways) to earn money.The shastras have allowed to do prathigraha even from the most sinful person (chandala) if not does not have money for his survival or To do vedic rituals like soma yaga.
In a nutshell,
If earning Rs.100 by vedic means(swadharma) is a mountain of sin earning by other means like being a engineer,doctor etc., is equivalent to 1 lakh mountains of sins.(as it is paradharma).
The Bhagavath gita says,
“Shreyaan swadharmo viguna: paradharmaath swanushtithaath|
Swadharmae nidhanam shreya: paradharmo bhayavaha: ||”
Even if ones swadharma has some deficiency it should be practised.Even if other duties (paradharma e.g. duties of kshatriya,vaishya,shudra) is well practiced it will not be considerd great as it is sinful.It is better to die being in swadharma since doing paradharma leads one to dangerous hells.
A brahmin must not work under shudras or mlechhas even during emergency.It is a great sin to work under a shudra.(e.g.Banks,Govt. jobs,MNCs, etc.,)
If brahmins cannot survive by above means the shastras allow them to do,
2) Pashu paalanam (Rearing animals)
3) Vyapara(Selling goods that are not prohibited by dharma shastras)
After the emergency period he should do prayashchitta and return to his swadharma.
Brahmins earning by being a doctor,singer, astrologer is considered very sinful.Brahmins should not run after money for luxuries.