Start with this Du'a
When someone offers you their wealth
بَارَكَ اللَّهُ لَكَ فِي أَهْلِكَ وَمَالِكَ
Barakallahu laka fi ahlika wa malik.
“May Allah bless you in your family and your wealth.”
Sahih al-Bukhari 2049
These are the words of the Companion 'Abd ar-Rahman ibn 'Awf when his brother in faith, Sa'd ibn ar-Rabi', offered him half of his wealth.