Inheriting a long term tenant that is paying late but catches up

[Ally Kumar]

I am buying a duplex and inheriting a tenant that has been there for 4 years, a single mom. It seems she is usually late with rent payments but catches up within few months. She is otherwise good tenant and keep her unit clean. Her lease doesn't expire for almost a year. I am new at this, any advice on how to handle this situation is appreciated. I have been listening to podcasts about being firm in my rules but this is an otherwise good tenant. Suggestions?