Thanks for the feedback. I hope i find an answer too and that thi queasiness in my stomach goes away. Mimi - he signed the original contract stating that I reserve the right to terminate if a client is late with a scheduled payment. The late payment fee is a new addition to my contract.
All of my other clients signed it without issue - they also pay me on time.
The worst case scenario is that I could always give him the option of adhering to the terms of the original contract and I could terminate the next time he is late with a payment.