Was this in America? Can you just do that, open a delivery restaurant on a whim? I'd imagine there would be all sorts of inspections and permits that would need to be acquired first before being able to sell one toasty sandwich.
Even if you skip it, it’s pretty low risk in short term, just dont make anyone sick/complain!
But there are also commercial kitchen spaces you can rent. They've taken care of the inspections and permits for the food preparation facilities. You pay an hourly rate to use the facilities. Then all you have to do is make sure that your employees have their food handler's permits (a simple matter) and you're good to go.