I want to buy a cow at low cost

For low cost, choose a healthy dairy cow, not a cheap weak one. Look for Sahiwal, Gir, HF cross, or Jersey cross. Milk her in your presence before paying. Do a CMT test on all four quarters. Ask which month of lactation she is in, because month seven or eight cows drop fast. Avoid cows above seven years. If the price is above fifty thousand rupees, take a Pashumitra or vet with you.