Denver is in USDA Zone 5, you want to look for plants that are hardy to Zone 5 or colder -- no mangos, but there's still quite a list you can plant.
You also need to look for plants that can handle a dry climate, though with a very thorough approach to permaculture you can capture the little rainfall you do get so that the plants get enough water.
Here's a list of pretty common plants from a quick walk through "Gaia's Garden" (p217++) -- which is worth the money to help you with planning your site. I used "The Backyard Homestead" for some of the yield information below, this is another decent reference for mapping out how to fit everything into a small yard. And some googling for other info. (Yields will probably vary widely from place to place, take it with a grain of salt.)
You should definitely look at some of these books for ideas beyond the few listed below. You'll want to figure out which will work well together as you build your guilds. And you'll need to keep mind precipitation amounts, timing, and the amount of water you can store in the landscape in mind as you're planning.
(You'll want (semi-)dwarf varieties where applicable unless you have a large lot.)
- Pear; mature dwarf pears might yield 1 bushel (50 pounds) per year
- Apple; A mature dwarf apple tree will generally produce 3 to 6 bushels of fruit. One bushel is equal to 42 pounds (source)
- Filbert/Hazelnut; 20-30 pounds
- Peach; Expect 30 to 60 pounds of fruit from a mature, well-pruned dwarf and 60 to 100 pounds from a standard sized tree. (source)
- Serviceberry; ?
- Russian Olive; 20 pounds per plant
- Hardy kiwifruit; 50-200 pounds per plant
- Grapes (look for extra hardy varieties); 10-30 pounds per vine
- Clover (N-fixer) -- for biomass and N-fixing
- Lingonberry; 5-10 pounds per 100 sq ft
- Jerusalem artichoke
A well-planned 1/4 acre lot, when everything is mature, could produce hundreds of pounds of fruit per year. I'm not sure about dwarf-size nut trees, but maybe you'll have room for something full size. Combine this with annual vegetables, some chickens if you can get through Denver's crazy permitting process, and you can produce quite a bit of food.
Lastly, watch out for zoning and HOA rules as you choose your new house.