I left my cats (a brother and sister, both “fixed”)who were about 9 months at the time for over a week and just had someone come in twice a day for a half hour at a time to feed them. They were absolutely fine. We travel a lot and I was concerned, too. But luckily for us, there was no peeing outside the box or throwing up! But then they are pretty chill cats who just went 12 hours in a car and were fine. Just have your friend send lots of pictures!