My thought is dont overkill/over spend time and money on the site just yet. I would put time and energy into the following initially...
- Good Inventory
- Good Merchandising
- High Visibility for the consumer (Craigslist, autotrader and cars just listing inventory)
- Online reputation
- telling your story
Content is only as good as your audience.... That being said content in our online world will create an audience (SEO/SRP, etc). While starting up you will be limited for content by inventory and as Joe mentioned time....
I would suggest focusing on merchandising - photos, descriptions and painting the picture online and getting these cars on third party sites where the reach will be dramaticly larger compared to spending energy on your website.
That being said everything circles back to inventory..... Even doing all the prior things you still have to have a desirable vehicle (according to the market)
As you grow it may be worth while to check out Vauto to manage your inventory, if nothing else to hear out their pphilosophies in how to handle inventory.
As inventory and online reputation grow I would suggest at that point to really dial in your website and activate additional marketing to drive traffic to that site....Just to clarify not saying that Dealer e process/dealer.com/ or custom vendor is the right way to go, just saying when it comes to online.....becareful over investing time and resources in your website while launching.
Good Luck Glen and Thank You for Your Service!!