Cooking food in a rusty pan is safe and the rust in the pan is not gonna harm you.
It's safe to eat food from a rusty pan.
Although when you coo food in a rusty pan the food may not taste as good because of the rust.
So it's recommended to clean the rust off the pan before cooking in it and lightly coat the pan with some cooking oil or some PAM cooking spray to prevent further rust.
At least just wipe the rust out of the pan before cooking food in the pan and you'll be okay.
Rust is actually healthy for you because the rust provides your body with some needed iron to keep you healthy.
So if you do happen to eat a bit of rust on some food it's not gonna harm you although it may not taste good.