well it depend on what you want to use the milk for. do you want high butter fat? if so i say nubians (but they are loud and love to test the fencing) or Nigerians dwarfs, they are small little things, the male are not suppose to past 28 (?) inches, cute little things, but will surely make sure that the place cannot be escaped from -_-. there is also mini breeds IE Mini la macha ( BTW the la macha is the only ear-less breed, meaning that they have no ears, they can still hear of course, and they are the most docile breed).
on the milk the goats gives out, it varies, the little Nigerian can give out at least a quart a day, will a Nubian can give a gallon, it depend on the breed, the breeding, and what the breeder is wanting IE are breeding for milkers or showers? the goat might have big lovely teets, but give out little milk if the breeder breeds more for showing.
on the feed it does depend on the co-op/feed store has, we feed purine goat chow, the alla natural stuff to our goats, with some extra stuff. and here is something to help keep the goat eating, Cinnamon! they LOVE it.
and shots, goats need shots like any other animal, you can save money by giving it your self, but the screams the animal does (not out of pain, more or less they dont like being stick, who would?) hurt the ears, and each month you need to trim the hoofs (which if you have a hubby, the best Christmas gift would be a milk stand

it makes shots, milking and all sorts of stuff easier!)
oh, before you buy contact your local group and check out about the breeders, until you get use to the goats, steer clear of CL and CLA herds, if you are gonna breed you dont want that on your land, it can take up to TEN years for it to leave. and the milk then would not be wise to drink raw.
and if you are gonna sell the milk check out your laws first! better to be safe then sorry.
if you have kids it would bea good idea to either get a polled (natural born with out horns) or a disbudded goat, or if you dont want to worry about your goat getting stuck In the fence hole because of it horns and maybe killing itself. .
and on the space 25 square feet per goat for lager, the minis will need less, wielded wire for fencing.
and also on the feed we have mainly junior goats, meaning they have not been bred yet and they eat less, will the goat giving milk (or is preggers) they eat more, and to get milk you need to breed, so that means baby, what would you do if you get a boy? ( hear goat meat is good *sorry, bad joke*)
your best bet is to get story guide to milk goats, it has great info, and it is a good place to start
i hope you will have a great time when you get your goats, we sure are!