铁杆庄稼

Traditional (Taiwan): 鐵桿莊稼

tiěgǎnzhuāngjia ㄊㄧㄝˇ ㄍㄢˇ ㄓㄨㄤ ˙ㄐㄧㄚ

    • business or source of income that will never fail

Character by character

Saying俗语俗語

Idiom惯用语 · Rarely used now

Literally
iron-stalk crops
Meaning
Originally crops that give a harvest in drought or flood; figuratively a business or source of income that will never fail or go under. Mostly approving.

Sources