I'm not too far away from the self sustaining generation, my fathers generation was the first to have a job outside of the family farm, my grandfather never held a job outside the farm but even he wasn't fully self sustaining, he sold animals and crops to buy things he needed. You need a lot of land and a lot of hands to work it, a lot of buildings and animals.
You need someplace to store your food, my family had dug out the side of the mountain and then walled off the front to make underground storage. Then you need to store the crops for the animals, barns for the hay, corn crib, oat bin, etc. You need a smoke house and/or place to salt the meat for storage. You need a wood/coal shed for haeting your home and/or barn. You need to have food and supplies stocked up in case you have a bad year or two to get you through those. You need to have a large family as a good% will die young and you need some to take care of you when you get old.