Shalom Alechem
Bab? kama daf 20a
One tossfot before the last one says that living in someone's home is Grama.
So comes out that if if a person has nowhere to live (Ze Nehene) he should be Patur, because even if he is having Hanaa still it is Grama.
Why If so (all Lefi Tossafot)
1) Ze Nehene ve ze Haser why is Chayav, is only grama?
2) What is the Gmaras question, -Ze Nehene ze ze Lo Haser. Pashut he should be Patur, also.
Tks
The Rosh here (Siman 6) explains that by Zeh Neheneh, you are Chayav since you are "eating" (gaining) from your friend's lacking (but regular Grama is hurting him without your gain).
All the best,
Reuven Weiner