Reference for Bava Metzia 129:1

דניחא ליה דלא נסתרי עבדיה

because he [the owner] is pleased that his slave does not become demoralized [through idleness]. But, he urged, that is only if one has no monetary claim upon him; since you, Sir, have a monetary claim upon them, it looks like usury. For R. Joseph b. Minyomi said in R. Nahman's name: Though it has been ruled, if one dwells in his neighbour's court without his knowledge, he is not bound to pay him rent; yet if he lent him [money] and then dwelt in his court, he must. He replied: Then I repent thereof.

Jastrow