From your letter, I see that you are not in the USA, and the amounts in other countries are less, as people eat more here.

It is quite difficult to go from 20 to 250 people. I would not do this as a first job.

For example, you are looking at at least 35 to 45 kilos raw meat; 25-30 kilos vegetables, 10 kilos dry rice.

Do you have freezer space to make ahead? Do you have enough oven space? Do you have refrigerator space to keep the food safe? Do you have the necessary license to make the food in your own home? If someone says the food made them sick, you can be sued, do you have liability insurance? It usually takes 4 cooks and a half dozen servers to make and box this much food quickly and safely.