I was wondering if you need to have more than one apple tree to produce fruit? I was thinking of a red delicious and a yellow one. I don't know how it works with fruit trees, I know the bees do most of the work, but I thought the yield may be better if you have more than one tree to help with the pollination? I don't currently have any fruit trees, but I have been really wanting to plant some apple trees.
You may want to look at "family" apple trees.
Some apple trees are self-fertile, and will give you something of a crop without cross-pollination, but all are better cross-pollinated.
There are four apple pollenation groups, A B C & D and, very simply, each will pollinate another apple of its own group and one in the group either side, so A will pollinate A & B; B will pollinate A B & C, C will pollinate B C & D, and D will pollinate C & D.
Some apples, such as Bramleys, are triploids, which means they need pollinated by two other apples or by a self fertile one.
So why would anyone want that?
Well, the apples tend to be bigger, the trees more vigorous, you get a bigger crop, and the trees are more disease resistant.