What food are you going to sell ?

There is no average can be estimate, as it based on the food taste, profit per plate and also location.

We can simple calculate the net profit by

Gross profit : Profit per plate (RM 2) X 100 plate X 30 days = RM 6000 per month

Rental : RM 800
Other expenses : RM 100
1 worker : RM 800

Therefore, Net profit : RM 6000 - RM 1700 = RM 4300 per month

Above just the the estimation as a guideline.