I believe there may be some value in a business like this, but you need to address the pain points in long distance vehicle purchases. The major hurdles to buying a used car out of state are:
1. Quality - how do you assess the quality of a vehicle that you haven't seen for yourself?
2. Price - how do you negotiate the price of a vehicle that you haven't seen for yourself?
Given that nobody trusts dealers or private sellers, there is an opportunity for you to be the buyer's trusted agent for a fee. You would probably want to arrange for pre-purchase inspections and even have someone available (you or a local partner) to inspect vehicles in person. There are already plenty of websites that list vehicles for sale and earn fees from dealers, so I'm not sure how creating another website is valuable.