A lot depends on the predators you have present. You don't really need a coop unless you have a potential problem with predators getting your turkeys as night. Then it's a matter of locking them up at night to keep them safe. You should eat least provide them with covered roost so they can get out of the sun during the day. They also need to have a place to roost at night where predators can't get to them. So if you don't have trees they can into you may need to consider a coop of some sort or a Pen/flyway.
Another item is in most states it's illegal to allow the release of domesticated animals into the wild. So you must have a strategy to keep them on your property.
What we do:
We have two turkey coops, one is an old chevy van that we gutted, the windows have been removed and replaced with wire mesh. It has a flyway that is 10 feet by 25 feet attached to it. The other is about 6 feet wide and 10 feet long with a pen that's 8 wide and 12 feet long. We do let them out during the day to free range for several hours.
I sold some chickens to a lady that used a 50 foot double wide trailer for her chickens.
I am a horse breeder. Somewhat retired do to my illness. I have lots of barns. My turkeys go into part of my barn that has a cement bottom. It looks like a tripple garage because it does have garage doors on it and a second story above it. It is meant for hay storage and is plenty big for lots of turkeys. I scrape it clean and rinse it down. Durring the day they are fenced with 6 foot horse fencing and a 6 foot chain link fence. One fence is not enough when it is breeding season. I need to keep the hens close or they will be lunch for someone. When it is not laying season they do stay close to the barn. Everyone is locked up at night and not let out until late morning.