When buying a used car, bring it to your mechanic before you buy the goddamn thing. I had to tell a good customer today that the 1989 F-250 he bought recently requires thousands of dollars to make it inspection-legal. The dipshit who owned it before him wanted to make it more hi-performance, so he ripped off all the emissions shit (air pump and accoutrement), replaced the factory exhaust with headers, and threw the catalytic converters away. He also replaced the Ford original equipment carburetor with a big ol' Carter AFB, good carbs but not the cleanest running units in the world. My customer bought the vehicle "as is" and has little recourse with the previous owner. So it's either pay me big bucks to restore the vehicle to its original configuration, or register it in a state without emissions laws. Good luck finding one of those in the New York Metro Area.
One of my rules you should write down. When buying any used car, have your guy check it out first before you lay down a dime. It'll save you in the long run.