SB 11.17.47

sīdan vipro vaṇig-vṛttyā
 paṇyair evāpadaṁ taret
khaḍgena vāpadākrānto
 na śva-vṛttyā kathañcana
Synonyms: 
sīdan — suffering; vipraḥ — a brāhmaṇa; vaṇik — of a merchant; vṛttyā — by the occupation; paṇyaiḥ — by doing business; eva — indeed; āpadam — suffering; taret — should overcome; khaḍgena — with sword; — or; āpadā — by suffering; ākrāntaḥ — afflicted; na — not; śva — of the dog; vṛttyā — by the occupation; kathañcana — by any means.
Translation: 
If a brāhmaṇa cannot support himself through his regular duties and is thus suffering, he may adopt the occupation of a merchant and overcome his destitute condition by buying and selling material things. If he continues to suffer extreme poverty even as a merchant, then he may adopt the occupation of a kṣatriya, taking sword in hand. But he cannot in any circumstances become like a dog, accepting an ordinary master.
Purport: 

Śva-vṛttyā, or “a dog’s profession,” refers to the śūdras, who cannot live without accepting a master. A destitute brāhmaṇa who is suffering intolerably may become a merchant and then a kṣatriya but may never take the position of a śūdra by working in a company or accepting a master. Although a kṣatriya is ordinarily considered more elevated than a vaiśya, the Lord here recommends that distressed brāhmaṇas first accept the vaiśya occupation, since it is not violent.