:)

Car dealers and salesmen both love the Payment Car Buyer. The car buyer that comes into the car dealership and buys a car based only on the payment. Most people would call this the Payment Car Buyer Scam, but not the dealer or the salesman. They consider this a transaction where the car buyer is more concerned with the payment than the price of the car or the interest rate they are paying. The job of your car salesman is to get you to focus on the payment. Many payment car buyers that have not done their homework when buying a car will do just that. They will get stuck by the car dealer scams.

Não creio que caiba "que negociam" porque qualquer possível negociação envolvida, não aparece na frase, ou seja, seria um elemento adicional (e, de fato, opcional).

Note também que, na frase simples "compradores a prestação", este "a" é uma preposição mas, se for adicionada o esclarecimento opcional "que só vêm", passa ser artigo definido.

sugestão