Hi Vinod,
glad to know that you are planning to start a dairy farming, but make sure to check below points before you proceed:
Do you have enough man power to start this business?
How far is your farm from the city?
Do you have 8 to 10 months of backup fund in case business runs down?
Have you praticial experience working in dairy farm?
Are you aware of most common disease and how to treat it?
Do you have own 3 or 4 wheeler vehicle to deliver milk?
What's the plan once Cow will be older? Will send it to slaughter house or keep it at farm itself? Remember Karma always pay back.
Hope this will give you clear idea before starting the dairy business?