I want to buy a dairy cow.

For dairy, start with Sahiwal, Gir, HF cross, or Jersey cross. First milk the cow in your presence, then do a CMT test on all four quarters, ask which month of lactation she is in, and check age, body condition, and vaccination record. If you want fifteen litres or more every day, remember one cow gives peak milk only in months two to three, so for steady supply you need two cows with staggered calvings. If the price is above fifty thousand rupees, take a Pashumitra or registered vet before paying. Treating a bad purchase now is far cheaper than losing milk for the whole lactation.