Welcome to BYC!
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Mountain Peeps has given you some great links to start with!
My personal favorite dual-purpose breed is the Wyandotte. Mine have been steady layers of around 250 eggs each per year, even though they are now nearly 4 years old. They have withstood cold temperatures below 0 degrees, and hot weather up to 104 degrees. I've never used them for meat, so I don't know from personal experience how good they would be for that. But, from what I've read, they are fairly good dual purpose fowl. My Wyandottes have had docile, though sometimes assertive, temperaments.
Dual purpose breeds are great if you want decent layers and decent meat birds. However, be aware that a dual-purpose bird will rarely lay as many eggs as a breed bred for egg production, such as a Leghorn. And, they won't grow quite as fast on quite as little feed as a bird bred for meat. They can make a great comprimise, however.
But, if you really want the least expensive eggs or meat production, keeping several breeds for their specific purposes may be best. For sheer egg production, choose White Leghorns, Black Sex-Links, or Red Sex-Links. These should all lay over 300 eggs each per year. For meat production, choose the Cornish Cross, or another special meat bird like the Freedom Ranger (which does better than the Cornish Cross when free-
ranging). Cornish Cross have been selectively developed for large, 5-pound birds at as little as 7 weeks old.
Keep in mind, also, that the best egg layers will not be the best brooders. If you want to have hens raise chicks, consider getting a special broody breed for that. Some of the best broody chickens are Old English Game, Cornish, and Silkies. But, these birds don't lay a lot. You can still use them to hatch the eggs of your other birds, however.
All of the dual purpose breeds should be good free rangers. But, the best free ranging chickens are the more wild ones, such as Old English Game and Phoenix. If it is important for your birds to get a large portion of their diet from free ranging, consider getting a hardier breed with better foraging ability.
Lastly, when deciding on the breed or breeds that you want to raise, consider the climate they are going to be in. For hot weather, it's best to pick breeds that originated in the Mediteranean area, such as the Leghorn, Buttercup, Minorca, and Catalana. These are heat hardy because of their large combs and wattles. For extremely cold climates, choose a breed developed for cold weather. Chanteclers, Wyandottes, and Buckeys are all great cold hardy birds.
I hope all this information helps! If you have any more questions, feel free to ask!