What you really want is an off-duty car
Off-duty cars have all the ingredients that make a cop car worth driving, but they also feature nicer, more conventional cloth seats, instead of the industrial-grade vinyl a police cruiser will tend to have. A chosen few even come with leather seats, but those are rare and generally given to county commissioners, chiefs of the fire and police departments, and other bigwigs. Not too coincidentally, these vehicles also have the highest frequency of diligent maintenance.
But don't assume that all patrol cars are junk
When you're shopping for any cheap used car, it really comes down to the maintenance and upkeep that the previous owner put into it. Some patrol cars are given plenty of attention from departments that have the financial resources and manpower. Suspensions are rebuilt, powertrains are repaired, and in many cases you can end up with a virtually brand-new vehicle for less than 10% of the cost.