I worked on a dairy farm as a teenager.
My best friends father owns it, so I it was mostly volunteer, but I did get a couple of pair of working show steers out of it.
They had milking Shorthorns. They are great as a dual purpose breed, also.
They are very hardy and do really well in winter. They are fairly docile and I think would be wonderful as a family cow. Unfortunately there has been a great decline in the breed and they are becoming very hard to find.
I would say a good fresh (just calved and producing milk) dairy cow would cost about $600-$1200 for a pure bred.
Housing can be quite simple, as long as they can get out of the weather they do well. Hay cost can be expensive but on the bright side is that cattle can extract nutrients out almost anything, so as long as the hay is not moldy, you can still feed it. Here hay is about 2.50-3 a bale. Although you can get it cheaper straight from the field, for about $1.50 as in you go out in the field and pick-up and load the hay the farmer just baled. A milking cow needs grain, about 3lbs is average daily. Usually cost is about $12 for 50lbs of grain. They will eat about half to 3/4 a square bale of hay if no pasture is provided. Really you can pasture a cow on one acre if the grass quality is good, and then offer a flake or two of hay.
So totals on feed w/ out pasture:
365 bales of hay @ 2.50$900 for hay
21 bags of grain per year at $12 a bag total $265
Total for feed+ $1165 per year
Add on vaccines, maybe $100 a year.
Really I don't think it's worth it unless you have good pasture...
Of course this is Maine pricing and your cost may vary...