I want a cow under fifty thousand.

For a dairy cow under fifty thousand, look for a healthy Sahiwal, Gir, or a good HF cross. First milk her in your presence, then do a CMT test on all four quarters, and ask which month of lactation she is in. A cow in month seven or eight can drop yield fast. Check age, body condition, and teeth too. If the deal is above fifty thousand, take a Pashumitra or vet along.