Housecats enjoy the fresh air and sunshine, so having a outdoor run that is built up off the ground and wired like a rabbit pen would be the best way to ensure the pets safety and reduce the change of it's escaping or other animals getting in the house. I have know of people who built a series of cat hutches in their backyard in a attempt to rescue stray cats and keep them from being killed by the animal control. However, it can become very expensive trying to buy cat food, plus keeping cages clean and protecting them from people, as well as, wild animals or dogs. But outside is better than having 50 cats in your house all running free. My ex-brother in law had 35 cats in his house and 27 in the garage. His house smells so bad that most people will not visit him.