Yes you can stay illegally in an apartment but you must register with the local police - also if someone reported you then you could get yourself in trouble. Also it is not safe to stay alone in an apartment with a stranger (he is a stranger like it or not) many women have been beaten or raped and I am not exaggerating!I'm honestly so confused with this. Because I asked this question in a Tunisian forum and everyone said I'd be fine to stay with him in an airbnb or apartment, that no one cares. And that Tunis is more liberal than most places in North Africa. Is this not true?
MH x