Divers are very specialized, they need deeper water (3 feet+) to practice their habits and they need a special diet as well, like Mazuri Diver Food, which contains specialized protiens more related to their natural diet.
And as Farmertank said, they are some of the most expensive wildfowl you will buy. Buffleheads and Golden eyes go for about $300+ a pair. I believe you can get mergansers for about $150-200 a pair and smews are around $500 a pair, then there are the kings of divers, eiders, which go for around $2500 a pair!! Canvasbacks go for around $200 a pair.
As far as what food to raise them on, Mazuri Waterfowl Starter or even gamebird starter would be good.
If you have never raised wildfowl i would start with woodies and teal, it will give you a feel. I wouldnt raise divers, buts thats only because i dont have the facilities to do it properly, but someday when i have a large natural pond, i am sure i will have something more specialized than what i currently raise!!
PS- Like farmertank said, you better check into your states permit regulations, most states require a permit to keep certain breeds of wildfowl, and if you intend on selling eggs or birds you will need a federal permit as well!!
