What rights do i have if served a 3day?

i live in a appartment complex and my rent is du on the 1st,afer the 5th of themonth a late fee is added. I recieved a 3day notice on the 8th . I called mangement and told them i could pay it in a week but tey tol me i will have to also pay attorny cost of minimum of $600. Are they allowed to do that?? does a late fee only cover 2 days?? what can i do?