Answer: their affordable monthly payment
Step-by-step explanation:
A potential buyer should avoid starting negotiations with automobile sales staff by establishing their affordable monthly payment.
When someone is talking with a car salesman, the person should avoid discussing the payment that he or she can afford. When one discloses their affordable monthly payment at first, this could end up having a negative effect on them as the salesperson could take advantage of the monthly payment offered if it's higher than what the sales person wanted to offer.