Responsa על בבא מציעא 128:5

Q. A young man lent money to A stipulating that the latter be responsible for the loss of it through theft, but not through unavoidable accident. The former also tutored A's son. In return for both services A paid the young man's living expenses. Is the lending of the aforesaid money considered a legitimate transaction?
A. If while the arrangement was made with the young man to rehearse the lessons with A's son in return for receiving his sustenance, the stipulation was made that the young man lend money to A, the transaction is considered usurious, even though A would have been content to pay the young man's living expenses in return for his tutoring alone. The fact that the money was not given as an actual loan, since A was not to be responsible for its loss through unavoidable accident, does not materially change the situation, since the Talmud considers the renting of money a usurious transaction (B. M. 69b). But, if it is true, what you write at the end of your letter, that the young man gave A his money as an outright gift so that he is at liberty, should he so desire, never to return the money to the young man, the transaction is a legitimate one.
SOURCES: Cr. 257; Am II, 151; Mord. B.M. 316; Tesh. Maim. to Mishpatim, 45; Agudah B.M. 88. Cf. Maharil, Responsa 37; Moses Minz, Responsa 72; Terumat Hadeshen 302.

Q. A young man lent money to A stipulating that the latter be responsible for the loss of it through theft, but not through unavoidable accident. The former also tutored A's son. In return for both services A paid the young man's living expenses. Is the lending of the aforesaid money considered a legitimate transaction?
A. If while the arrangement was made with the young man to rehearse the lessons with A's son in return for receiving his sustenance, the stipulation was made that the young man lend money to A, the transaction is considered usurious, even though A would have been content to pay the young man's living expenses in return for his tutoring alone. The fact that the money was not given as an actual loan, since A was not to be responsible for its loss through unavoidable accident, does not materially change the situation, since the Talmud considers the renting of money a usurious transaction (B. M. 69b). But, if it is true, what you write at the end of your letter, that the young man gave A his money as an outright gift so that he is at liberty, should he so desire, never to return the money to the young man, the transaction is a legitimate one.
SOURCES: Cr. 257; Am II, 151; Mord. B.M. 316; Tesh. Maim. to Mishpatim, 45; Agudah B.M. 88. Cf. Maharil, Responsa 37; Moses Minz, Responsa 72; Terumat Hadeshen 302.