Owning Horses

My family and I have recently moved to a rural area. We have 10 acres of land and are looking to expand that. My wife has experience with horses when she was young and my children are taking riding at a nearby farm.

What do I need to know good, bad, and in between about horse ownership. No firm decisions are being made and there will be long discussions after. I’m just wondering what would you have wanted to know before getting a horse/ horses?