I suspect the capital costs of this would make the business unsustainable. The company would have to maintain essentially a dealership sized inventory of cars,

I suspect the capital costs of this would make the business unsustainable. The company would have to maintain essentially a dealership sized inventory of cars, but instead of having the revenue stream of car sales they'd just have to rely on this test drive fee. How many $20 test drives would people have to take in order to offset the costs of buying millions of dollars worth of cars?