Tina, just make sure that you ARE prepared to "do the deed" before you get the birds - especially if you get cornish crosses, or meaties. They are not meant to live past 8 weeks, and can die under their own weight. Some get so big so fast that you have to slaughter them much earlier. The heritage breeds are just fine as long as you're not looking for an oven-stuffer roaster. The Salmon Faverolles (my favorite breed) is the national chicken of France, and there are certain meat dishes there that can only be made with that breed. The Wyandottes and the Rocks are your classic heritage bird - what do you think our ancestors ate before they invented these horrible franken-chickens? How about our own At least with the heritage breed, although you may end up with a slightly lighter carcass, you'll get good flavor, and a bird that won't eat itself to death. Check out the list from Slow Food USA - there's no cornish on it. This is a list of the most flavorful and fulfilling foods you can grow and eat, even if you have to wait a little longer.
http://www.slowfoodusa.org/index.php/programs/details/ark_of_taste/
For more info on slaughtering, do searches for Harvey Ussery and Joel Salatin. They have it down to a science, and with methods that can be replicated at home.
Good luck!