You don’t need a back 40 to grow a fruit tree. You can buy columnar apple trees bred to grow straight up like an exclamation point. You can grow one tree with several varieties of fruit grafted on it. You can grow trees attached to dwarf rootstock so they stay small.
You do need a sunny spot and well-drained soil. Other things to know:
1. Pick a tree with dwarf rootstock. Nearly all fruit and nut trees are grafted to another tree’s root system, usually to control size. Look for trees with rootstocks of M.9 or M.26. The growth of these trees is generally 4 to 8 feet tall.
2. Pick a variety that tastes good and grows well here. Sorry if you love Red Delicious but this apple doesn’t do well in Western Washington. Consider, too, how resistant it is to diseases and pests. Fruit that does well here: http://gardening.wsu.edu/library/best002/best002.htm
3. Most apples and pears and some cherries won’t produce fruit unless they are pollinated by another variety. To complicate matters further, the bloom periods of the pollinizer varieties must overlap too. You can ask a specialty nursery for help or you can figure it out yourself by checking pollination charts: www.raintreenursery.com/pollin_home.html
If you plan it right, you could have one apple tree with several varieties grafted on it that pollinate each other. Yum.
More on the best kinds of fruit to grow: http://mtvernon.wsu.edu/frt_hort/fruit_horticulture.htm.