This is to state that although I was very impressed with the functioning of the <city
name> Chamber of Commerce, yet I am sorry to decline your invitation to join it. I was
very impressed by the group's professionalism, ideas and commitment to helping local
businesses grow, but since I am in the business of <your type of business>, I don't
think the Chamber would really help me grow.
I would like to reiterate that I have immense for what you and the other members are
doing, and I wish you only the best of luck in your endeavour. If my business
circumstances change, I shall certainly contact you about joining. I would extend my
thanks for informing me about the Chamber.