My quick advice to all those questions is go slowly. Don't buy all your stock all at once, you can always get more rabbits later. Get quality, not quantity. Leave some room/cage space to change your mind later.
1. Only start with three, a breeding trio, the best buck and two does you can afford. A long car ride to get an $80 dollar show quality buck and two $40 dollar does will be better than 6 $20 mediocre rabbits. Get quality not quantity. If the babies you breed come from quality stock you hopefully will get your money back when you sell the quality babies. Also, spend more money on the buck because, if you are lucky the buck will breed for 5 years or more, and you can always resell them to other breeders even after they are a couple years old if they are show quality and proven, but the does can stop breeding after 3 years, and you can't really resell them after three years. So the quality of the buck is the most important. You need two does because you always breed the does at the same time, incase one abandons her litter or has a single kit (which will freeze if left alone in the nest), you might need to foster to the other doe.
2. Does should not live together, too risky, there's a small chance they will get along if raised together as babies, but once they get hormonal they get very moody and territorial and you can't underestimate how vicious they can get... they can kill each other, plus vet bills. To be safe you need separate cages for each doe.
3. There are certain colors that go together, Here is a table chart that tells you the colors.
http://www.angelfire.com/mi4/bunnyrun/COLOR.html
4. I would either get the chocolates, or the blacks and otters but not all colors all at once. (check compatable colours chart link above). Pick one color and only get 3 in the color you like best, again "Buy quality, not quantity" go slow like I said above, and Learn from the first three rabbits you get. They will keep you plenty busy. Once you get their set up perfect and the way you like it, then make plans to get more. Once you buy your first rabbits you will probably see other rabbits out their that you wish you would have gotten instead. Trust me, I bought Otter Nethies when I first started and then I saw a Blue eyed White rare nethies for sale, so I wanted those, and then I saw Jersey Woolies and wanted those instead.... once you start breeding rabbits, something better always comes along that you wish you would have gotten instead... you change your mind, and then you run out of cage space.
Also, go slow because when you get your rabbits, unexpected things happen, like mysterious unexpected illnesses no one can figure out, and vet bills, and stuck kits, abandoned kits, and racoons... and did I say vet bills.
Also, you may already know this but....
With Nethies you need to read all about the dwarf genes first, and understand the genetics of peanuts and why they happen before you start buying stock. You definitely want a true dwarf buck, but you might want false dwarf females (BUDs). And you definitely do not want a false dwarf male (BUB) and true dwarf females. So, before you shop for your stock you should know all about the genetics, and the following terms... true dwarf, false dwarf, BUD, BUB, peanuts, hippo, max factor, stuck kits.
:bunnyhop: 
