Several things come to mind. First, take a look at this post-
The post is reply to a person that was starting an orchard similar to what you have in mind. I would also look at the entire thread as he got a lot of feedback from a bunch of people.
Second, do as much research as you can before you plant anything. Tree spacing, rootstock and cultivar can’t be changed easily once the trees are planted so you want to get that right in the beginning.
Third, buy a few trees. You may get some excellent advice on the forum but no one here has planted trees on your land, in your climate, and in your soil conditions. That means you orchard is a new experiment and what actually will work won’t be known until after the fact. You want to get a few trees maturing quickly so you will learn what pests and diseases you will face. Buying trees will speed up the learning process by 2-3 years. Some problems like fruit cracking and Summer rots are very dependent on the cultivar of the apple and local conditions. You want to avoid planting large numbers of trees that don’t produce a good crop because of these problems. A few early planted, purchased trees will help you avoid the problem. Here is post that talks about planting a few trees to help learn the what the local conditions are like.
Personally, I would buy say 4-8 trees and then graft 20-50. You will learn a lot from these trees and the grafting experience but at the same time you have a smaller more manageable time commitment. You will make mistakes and have bad luck (I know from experience lol). But since you have fewer trees and grafts these setbacks will not cost you much and fixing problems in a small orchard is easier than doing the same in a large orchard.