Fruit trees are certainly a $25 tree and a $20 hole sort of deal. Weed barrier, trunk protection and a wire cage with support is all needed to ensure the deer don't prune your tree for you. You also need to ensure they will get plenty of light, and stay away from low lying areas. Low areas tend to collect cool air and can kill the flowers in the spring resulting in no fruit. As for the trees themselves...make sure you select a rootstock that is good for your are and will grow the size of tree you want. Smaller (dwarf) trees will tend to fruit sooner but tend to leave a lot in reach of the deer. Standard trees will grow much larger but tend to take a little longer to fruit. I plant semi-dwarf root stock, and when the trees are older I can trim with a pole saw while standing on the ground. I also then train my trees so the lowest branches are 5 feet or so off the ground if I can. Other than that...pears and crab apples seem the be the easiest to grow from a disease and pest perspective. You will also want to find out what ripens and falls in your area that works for your needs. I avoid "summer" apples because I don't hunt in the summer. As for typical apples there are a bunch of different varieties out there and it all depends on what you want. There are some real good resources here to help guide you.
Do NOT buy fruit trees from a big box store....many times you have no idea what root stock these trees have and in most cases the varieties they carry are "people" apples....which is fine if that is what you want. Most of us want apples for the deer and thus we want them to drop during our hunting seasons. Find a reliable source for your trees that is near your area and they can walk you thru what should work well for you also. Lots of folks here have used many of the bigger on-line nursery places so they can help you with who is good and the like as well. I personally use Turkey Creek Nursery (TC is a member here and will walk you thru the selection process if you so desire).