On my quarter-acre lot in California’s San Joaquin Valley, I have about 50 small fruit trees (citrus, apples, peaches, nectarines, apricots, plums, and cherries) grape vines, blueberries, blackberries, raspberries, strawberries, squash, cantalopes, watermelons, tomatoes, eggplants, rhubarb, Armenian cucumbers, potatoes, carrots, basil, parsley, tarragon, and a kiwi vine. (And there is plenty of space left over for the house, garage, ornamental landscaping, and plain old lawn, although more of that lawn is going away next year, to be replaced with more fruit trees.) Now, I didn’t do it myself; I paid my gardener quite a bit of money to build trellises, install drip irrigation, break up hardpan [adobe clay soil] with a jackhammer, replace bermuda grass lawn with planting space, prune the grape vines, and generally give me advice. But I couldn’t do it myself, and I regard the money as well spent, not only for my own benefit, but to help employ a good, honest, hard working man with a family to support.
But my point is: you can grow [dwarf or semi-dwarf variety] fruit trees as little as four or five feet apart; you just prune them ruthlessly when they get too big. The Dave Wilson Nursery web site  is very helpful.
My other point is, besides non-perishable food and necessary household items, I am buying extra fertilizer. The price is quite a bit higher this year than last year, and I expect it will only get higher in the future.
– K.C. in California