Some people who know little about cars, go to see one that is for sale. As they don't know what to check, they kick the tyres hoping that this will initiate a magic spell that will tell them whether the car is worth buying. In reality it will just tell them that there is air in the tyres, but not how much. Often the term 'tyre kickers' is used to mean the same thing as 'time wasters' and they may not have any serious intention to buy the car. In the passage quoted, the person had made a cursory inspection of the place and found the condition and upkeep to be less than satisfactory.