A cloud kitchen has no dining area. You cook in a rented or shared kitchen and deliver to customers yourself or through delivery apps. Focusing on office lunches in one neighbourhood keeps the menu short, the delivery routes tight and the daily order count easier to predict.
Start with a small fixed weekly menu and sign up a few offices for a trial before you buy equipment. You need FSSAI registration before you sell food, and possibly a local trade licence. The cost range is a rough estimate for a small set-up; rent, equipment and deposits vary a lot by city, so price it locally before you commit.