As the owner operator of an auto auction for nearly a decade I can honestly say that the uninitiated should NEVER buy a car from an auction house. Here is a short article on why that is. For starters MOST of the auction houses are directed towards auto dealers. There are nefarious people in the industry and abroad that have been known to poorly repair, or cover up parts that need repair in vehicles and then run them through the auction to get rid of them. I refer to this as "lemon laundering". For instance, if a car has a blown head gasket it will exhibit no signs, aside from a coolant light, for about 3 minutes of run time before it starts knocking terribly. So lets say someone bought a car with a bad head gasket and they wanted to get rid of it instead of eating the cost of repairing it. They could run it through an auto auction, where the car would quickly be started and run through the lane without anyone knowing, especially if they clipped the wire to the coolant light. If the sale is a red light sale, then the new owner is stuck with it regardless.
Lets say a car has a an automatic transmission that is on it's way out. This typically means it slips when it's warm. It's very easy to fill the transmission with something very thick to keep it shifting for a few hundred miles. I have seen substances from Lucas to Oatmeal.
I have seen JB weld used to patch holes in engine blocks, I have seen a corolla that was cut in half and another corolla cut in half and both of those halves were welded and caulked back together and you couldn't tell from the outside. I have seen spark plugs blown out of their cylinders with Epoxy holding the plug in just long enough for a sale. I have seen a lot of truly awful, unsafe body work. These are the kinds of things that car dealers are trained to look for and they get fooled a good portion of the time. They end up eating the cost of the vehicle on these things and they build that into their pricing. The average person hasn't got an ants chance in hell of seeing some of those things until it's too late. Do yourself a favor and buy from a respectable dealer that has good reviews. Leave the auctions to the professionals.