Rent is due on the first every month and if it is late there is a thirty dollar late fee. I want to know if there is some kind of law saying that a person can be a day or two late without being charged a late fee?

I don't think there is such a law. If you going to be late you should contacnt the landlord right away if it is your first time they might wave the fee.

This is a matter of contract. A grce period can be written into the contract. Late charges are also written into the contract. Whatever the contract says goes.

If you and the LL both signed off on a late fee then a late fee it is, period.