I have seen aggressive sahiwal cow which used to attack if you are standing showing back of yours. The aggressiveness will vary from animal to animals.
But if you have enough patience and commitment and lots of LOVE towards cows you can make them sadhus yes it takes time.
Kankrej cows cost is less and maintenance is very affordable. Once they adjusted to you or your family they are like small babies. They yield any where between 5 to 18 ltrs based on the maintenance of the cows.
If you can travel to south I will suggest puganur or Malnad cows. These are dwarf breed of desi cows. Very much adaptable to any environment and produce 2 to 4 ltrs. The cost is also very less. Maintenance is very less, their fat content is 8%
You have to buy 3/4 cows and a bull so that your mild need is full filled through out the year.
If you want to have desi cow milk for your family all time, then you require 2 to 3 cows based on lactation period/heat/pregency.