These Hebrew sites cite a letter from Rambam to Eliyahu the Dayan (Igrot Rambam, Rav Shilat Press, Volume I p. 311; emphasis added):
והרעה הגדולה שבאה עליי באחרונה, ...והיא פטירת הצדיק, שטבע בים הודו
ובידו ממון רב לי ולו ולאחרים והניח בת קטנה ואלמנתו אצלי..והוא היה האח. והוא היה התלמיד
והוא היה הנושא ונותן בשוק ומרוויח, ואני הייתי יושב לבטח...והלך לחיי העולם, והניחני נבהל בארץ
And the greatest tragedy that recently befell me was the death of the righteous one who drowned in the Indian Ocean while holding a great deal of property of mine, his, and others', leaving me with his young daughter and widow, namely my brother. He was a student, he would do business in the markets and make profits while I dwelled securely ... he has gone to Eternal Life, leaving me confounded in a strange land.
So his brother had "money of his", "and did business while leaving me secure." I guess there are several ways that can be read:
- He had money that he had -- pledged to me? Owed me? Because he was supporting me?
- He had money that I had invested with him.
- He "left me secure" because he paid all the bills, or because he took care of the major risks?