not taking sides here at all..but it is a used unit.things go bad..it doesn't matter how much you look and kick the tires when buying a car you can not predick when and if things are going to break or wear out.i was a service manger years back at a ford dealership and we had new cars that would break on car hauler so had to fix them just to get them unloaded.you can not tell by looking when something is going to break.
there is guys on here that puts me to shame on how much they know and there fabications skills and i'd put money on it that not one mech/builder can test drive a car and tell you that the trans will go another xmiles before it breaks or a water pump will start leaking in 2 weeks.
remember 1 thing..these are cars/trucks and they can break at any time..
i do understand your concern..that is a lot of money to put out for something then get home with it and got to spend money on it already..but if everyone thinks about it..how many times has this happen to each and everyone of use?that is way we sell things AS IS...we can tell the buyer that nothing will go wrong for the next 60 days..it can't be done..