I kept chicken for 25 years and never noticed any chickens with two heads or 3 feet. I don't think its an issue. We never had just one kind of chicken so, more genetic material to choose from.
Araucana and Cochins were always our favorites. Of course, every year, someone would fall in love with a new chick at the feed store so, there was always an infusion of new blood, usually something silly.
If you are doing this because it sounds like fun, go for it. If you are doing this because you think it will be easier than buying eggs from the store, don't. Its expensive and time consuming to raise chickens. If you want fresh eggs, find someone with chickens and offer to buy some.
Chickens don't start laying until they are about 6 months old, just in time for their first molt and winter. No eggs when they're molting or when they're cold. You will need a coop and a coop yard with a 6 ft. fence and a roof, otherwise you will lose them all to the first coyote, fox, raccoon, possum, mountain lion, hawks, the neighbor's dog... (we lost chickens to all those animals).
This is not to discourage you, I loved my chickens, ducks and geese. Its just a reality check.
