Dentist wants me to get crowns - I can't afford this?

Let's just say at a very young age (roughly between 12 or 13 years old) I started drinking coffee, heavily. Now, at 24, my two front teeth lost most of their enamel and they're not in great condition from grinding, too. They're smaller now and lost their natural color. My dentist wants to do porcelain crowns on those two teeth. Would it be bad to ask my dentist for a more affordable alternative (like composite veneers) until I can afford crowns?