The apple tree advice is good advice, and here are a few additional thoughts. You have to plant trees that cross pollinate each other or you will get no apples. Simplistic advice says plants a different kinds of trees, but that might not be enough. Not all apple trees pollinate other apple trees...the reason is twofold. One, they need to flower at the same time. Two, there are genetic reasons why some trees simply will not cross pollinate others. So ask someone who knows and be sure. Another thing to consider are crabapple trees. Many are great pollinators for regular apple trees but best of all many, if not all, do not require another apple tree...they are self pollinating. Finally, if you are planting regular apple trees they need to be in proximity to each other. Orchards recommend about 20 feet...so if you are scattering trees around 100 acres, like I did, you can concentrate some in an orchard and ensure proper spacing and plant crabapples in other locations and not sweat it. I’ve mixed crabapples in with my regular apples to enhance pollination opportunities. Good luck, and be patient because it doesn’t happen in a year or two.