[The411]

My Suggestion is to cash in your current car (If you have more than one, you could have a 'specific place' to park your car) then you cash it to 'get' another car for about...

$1000? Less or more, thats my suggestion, say if people want to have a new color of a car.

Basically,

Player A has Two Cars,
Player A puts CAR A into a part of the Car Dealership called "Exchange"
Player A Clicks on a new car and buys it for $1000(more or less)
Player A still has CAR B and exchanges CAR A For a new Car.