In the car business...that store is usually referred to as a "pot lot". They acquire most of their cars from auctions that dealers send the cars do not meet their requirements to. These cars usually consists of ones that have too much problems that the dealer does not want to or cannot fix and still make a decent profit. The others ones are usually cars that have been wrecked and sometimes with frame damage.
I usually advise people to stay away from these types of "dealerships" as they are the ones that give the car business a bad name more than anything.
Why did you not have a PPI done before purchasing?