SB 11.17.49

śūdra-vṛttiṁ bhajed vaiśyaḥ
 śūdraḥ kāru-kaṭa-kriyām
kṛcchrān mukto na garhyeṇa
 vṛttiṁ lipseta karmaṇā
Synonyms: 
śūdra — of the śūdras; vṛttim — occupation; bhajet — may accept; vaiśyaḥ — a vaiśya; śūdraḥ — a śūdra; kāru — of the artisan; kaṭa — straw baskets and mats; kriyām — making; kṛcchrāt — from the difficult situation; muktaḥ — freed; na — not; garhyeṇa — by that which is inferior; vṛttim — livelihood; lipseta — one should desire; karmaṇā — by work.
Translation: 
A vaiśya, or mercantile man, who cannot maintain himself may adopt the occupation of a śūdra, and a śūdra who cannot find a master can engage in simple activities like making baskets and mats of straw. However, all members of society who have adopted inferior occupations in emergency situations must give up those substitute occupations when the difficulties have passed.