MB4 252b: Acquiring Rights to a Jointly Owned Chatzeir - part 2 (382:17-19)

An eruv chatzerot in a courtyard with access to the outside only via an outer courtyard (e.g. an apartment building):

If a gentile lives in one and Jews live in the other one they need to acquire rights from the gentile since he has דריסת הרגל in the outer courtyard.

If a non-Jew rents his house to another non-Jew from whom do the rights need to be acquired?