I tend to agree on the "don't test drive unless serious" opinion, but I will be facing a similar dilemma soon. I will be moving to a new town and we'll be getting a 3 car garage for convenience and forward compatibility with a potential sporty car down the line. While I don't plan on buying a used 911 now, it is on the cards for a few years from now when stacked up against the C7 Vette and F80 M3. I do plan on test driving a used 911 sometime soon and won't have any qualms with adding mileage to whatever is there from the first owner. I do want to know what is the least powerful engine that I would like and how the car fits me before I dream about what I want and keep an eye open for the properly priced and equipped example to show up on the market when I have the money ready.
I will also tell the salesmen when I am just starting the car search, as I like to test 2-4 competing models before buying. Therefore I don't usually buy on the first visit. If the salesman tries to pressure me after the drive to buy, I feel less motivated to give him the business. If he pushes, I will actually haggle to see how low I can get him before leaving. After all, I warned him that no purchase would happen that day but he went by the pressure cooker sales recipe.
I will also tell the salesmen when I am just starting the car search, as I like to test 2-4 competing models before buying. Therefore I don't usually buy on the first visit. If the salesman tries to pressure me after the drive to buy, I feel less motivated to give him the business. If he pushes, I will actually haggle to see how low I can get him before leaving. After all, I warned him that no purchase would happen that day but he went by the pressure cooker sales recipe.