Milk breeds tend to produce WAY more milk than a single calf can use. This is even if you milk her once a day.
And let me tell you from experience, that there seem to be VERY FEW bottle calves in beef breeds. They don’t take them off their moms because calves gain so MUCH BETTER. We found exactly ONE heifer calf, in hunting HARD for a beef calf over 2 months! We bought her but she was already 2 months old and cost $400. Maybe we didn’t have the right connections, but NO ONE we talked to would take a beef calf off the cow, didn’t have orphans. Beef practices are totally unlike Dairy farmers.
You could probably pick up a couple dairy calves easily from a local farmer, to put on a cow to keep her cleaned out. Or breed her for a calf, then add on a second calf in a couple weeks, so she is feeding two.
You have to be careful that the dairy cow gets ALL THE QUARTERS of her udder milked clean daily. Single calf may or may not do that. I have heard of a calf only liking 1-2 quarters, never nurses from the others which develop severe problems. Little calf just can’t drink what dairy cow produces, way too much milk. So any dairy cow is going to need attention more than “now and then” when YOU need a bit of milk. If you don’t care for her properly, provide extra calf for instance, you take the chance of ruining her udder, her getting sick.
Not sure if you would want to raise a beef heifer, then just milk her once a day, to share with her calf. Beefers probably produce as well as old-time milk cows did way back. Beef cow would have a smaller udder, but still could give a gallon or more, with once a day milking. You pen up the cow and calf overnight, separated. Then milk her first thing in the AM when she is full, calf can eat all day. I am suggesting a beef heifer, they are pretty available, naturally have a smaller udder so less worries about mastitus or other issues with a constantly overfull udder.
The more you milk the cow, calf or calves empty the udder, the more she will produce. When the demand is on her from you and calves, she will give more milk. She will need PLENTY of nice water, good amount of hay or grass to produce this milk. Grain amount will depend on how good the grass and hay are. Grain will get her into the stanchion for milking, keep her friendly.
If you have not trained a cow to milk, finding one that will stand for hand milking is IMPORTANT. Cull cows from the dairy farm will only be used to equipment, though they can be retrained to hand milking. Sometimes the Amish have cows advertised that will be hand milked. Hand milking is work, with effort to totally strip the udder quarters when you get finished.
You will want to get her TB tested before purchase, to prevent buying a problem for your family. Most States require that annual testing in dairy herds, before milk can be sold to the Co-Op.
And lastly, are you prepared to do the work of milk preparation so it is ready to drink? I STRONGLY suggest you DO NOT just drink the milk from the milk bucket. You can look up what steps are needed to prepare milk before it is “family ready”. I do suggest you read up on what benefits are gained by pasturizing the milk. Personally? I WOULD ONLY drink pasturized milk or serve it to my family!! Lots of Raw Milk enthusiasts touting the health benefits, but some of the stuff that is in/can get in to raw milk will kill you! A number of news stories on that very problem, buying and using raw milk recently, kids died. Cooking the milk to needed temps for pasturizing, for length of time needed, is going to remove the chance of problems.
Getting a milk cow of any breed, using her for milk, is not a decision to be taken lightly. You really have to be committed to the whole deal. If you only do what is “convenient” to you, cow will get damaged, your family will probably end up sick. Cows are absolutely run by a clock, want things done in strict routine if possible. So milking at the same time daily, EVERY DAY, feeding at the same times, is IMPORTANT to the cow. She will cooperate if you abide by this. Skip a day or two, she isn’t going to be so cooperative. Cows and milking them, processing the milk is a TIME investment thing. Seems like any shortcuts don’t work well. Not like having goldfish.