When we were first married, we only had one car, and it was SUCH a budget choice! We lived way out in the country, so no public transportation, no taxis, nothing. It was rarely a problem, and it was really the thing that allowed us to start out saving 50% of our income while we were young -- it's really the reason we were able to put aside money while we were still young enough for compound interest to make all the difference.
Pitfalls? None.
My suggestion: Ask him to give it a year's trial, and if you're not happy, they'll still be selling cars. Or, if he balks at that, suggest that you freeze the car key so that it's not readily accessible ... and see how long it is 'til you actually NEED that second car.