I bought a 1994 Jaguar XJ6 on Ebay from a fairly local seller of Classic cars.
Supposedly everything was working perfectly. The ac, the doors, heater, locks, the sun-roof, cooling system etc..
When we went to collect the car, and he was not available until the darkness, evening, the doors were open ,the engine was running, and he mumbled something about a lock had stuck. The car looked and sounded great.
I was tired so I just wanted to get out of there - I did not discover until a few days later what needed to be fixed. The AC, auto locks, heater, drivers door seal. After 2 drives the battery went flat, the check engine light came on, a belt was screeching, the ignition light never went off.
Thank goodness for Haynes. How to fix all of the above right there in the palm of my hand. Now I can start fixing the heck out of the car. To own a Jag is to work on it and to work on it you need a Haynes Manual.