I have had apartments nearby provided by families before and that is the best situation of course. I was a true "live-in" once for less than a year and it was not enjoyable. Like the PP said some of the issues were noise, hearing people outside your door was awkward and since you weren't family it seemed like I should keep my door closed so it could truly be my space. My family was two young school age boys and they always wanted to play, you never are truly off unless you are going to be really strict and then you would probably have an even stranger relationship with the family.
Eating, cooking, etc was also strange. If there were dishes in the sink, especially only 2 or 3, it felt really strange and petty to just wash my plate and cup and leave their things there. Especially if I had to lay out a towel to dry my things it was so awkward to think of leaving their dishes in the sink.
Storing food, even if you share nothing, just seemed strange.
I also never invited anyone over except on days I knew the family was going out for a long time. They would tell me their plans and I would plan my life around house availability.
Never again, if they aren't offering an apartment I won't consider live-in.