If it doesn't have an ag listing you won't be able to put livestock on it, regardless of the amount of acreage.
If it's in a subdivision, I can tell you right now you won't be able to put horses on it.
Besides, why would you want to put up fencing on a rented property? You're only increasing the value of it for the owner, not yourself.
Before you and your family get all gung ho about a particular place, you'd better find out what the covenants and restrictions are, as well as whether or not you can put horses on it.
Never trust what a R/E agent tells you concerning livestock; always do your own research.