Good morning! I've been raising kiddos all my life, but I'm a newbie with chickens. My girls are nearly a year old and are doing great in what's basically a covered run. However, We've recently moved to the country so now we can build them something permanent. we want to let them free range for sure, but with a small run for when we're not at home. we're looking at coop designs and wondering why some are raised off the ground and some are not. Can someone educate me on the benefits of each design, please???? Thanks so much. I need lots of guidance.