Dua for Expanding Rizq (Provision)
اَللَّھُمَ اجْعَلْ اَوْسَعَ رِزْقِکَ عَلَیَّ عِنْدَ کِبَرِ سِنِّی وَ انْقِطَاعِ عُمُرِی
O Allah! Expand for me Your provision till my old age and till the end of my life.
This du’a is graded weak, but suitable for recital.
(Mustadrak Hakim, vol.1 pg.542)
However, the part of the translation that I’ve highlighted in your question is inaccurate.
The correct translation is:
O Allah let your most abundant provision for me be during my old age; when it is the end of my life.
This is a du’a for protection from poverty in old age, which -obviously- should be recited before old age.
For general increase in sustenance, one may recite the sunnah du’a:
Allahumma inni as-aluka ‘ilman nafi’a wa rizqaw wasi’a wa ‘amalan mutaqabbala.
Also see here.
Click here for more on how to repel poverty/debts.
And Allah Ta’ala Knows best,
Answered by: Moulana Muhammad Abasoomar
Checked by: Moulana Haroon Abasoomar