Don’t let a possible sale override your integrity and ethics. You’ll get potential clients who will be disrespectful and demanding before an order is even placed. Don’t bite your tongue throughout a negative experience as they can mark an order as a negative review for nothing. Even if you were kind and reasonable, these things do happen.
Ask a lot of questions before sending offers, and see if things can work out. If you believe that it can lead to a negative outcome, it’s OK to professionally decline service. Compromise and communication is the key, but don’t let a morally challenged individual take control of your service.