Do you really need to have the car physically in order to sell it? Can't you just have a comparable display model that is used for test-drives? When sale progresses, then you can show them the actual vehicle and sell it to them for a discount.
And if it’s a used car dealership or a dealership that accepts trade-ins, there’s going to be a handful of models in single quantity.
You also have a very diverse lineup on a used car lot, so the odds that you have something legitimately comparable is very low.