Okay, I'm carving this up into manageable bits for you to read, digest and enjoy; or at least use an excuse to use your nausea medication. Car dealers and curbstoners (those people who buy cars and fix them up to sell) have your number the minute you enter their domain. They're going to portray that vehicle in the best light possible and even a reputable dealer isn't going to know the history of same. To make matters worse, they're going to clean out all those receipts and service records and steam clean all those pesky oil drips from underneath.
I've even heard of people buying a truck, removing the interior, and the odometer, driving it to death, and then re-installing the odometer and interior that look brand new. Ideally, you should take the car to a mechanic not in cahoots with the dealer. He or she should look for problems and will charge you some money for the service, but will be well worth it. If you want to do this on your own, you're crazy, but it can be done. First of all, check the tires. If they're brand new on a two year old car, the alignment is likely off due to frame damage or other problems. If the tires aren't new, check the tread for evenness and make sure the wear bars aren't showing (they're perpendicular to the tread if the tire is worn). Any uneven wear means that suspension parts are worn or the frame is damaged. Look at the underside next for rust and rot (anywhere salt is used to deice roads).
You're also looking for new or broken parts. On a two or three year old car, the exhaust, steering and suspension should be original to the vehicle and have the same patina as the rest. Ball joints and tie rods usually, but not always last at least 100,000 miles and the originals will not have grease fittings (this is the industry standard). New parts could mean more wear or miles than the odometer might suggest (In Michigan, where our roads are the pits, it could also mean normal wear and tear). Exhaust systems usually last at least 200,000 miles or more, so new exhaust parts mean the same thing.
While you're under there, look for any parts with "junkyard tattoos." These are those yellow marks made when parts are purchased used and also denote wear outside of the norm. It could also signal damage that the dealer or someone else is trying to cover up.
Starters, alternators and other parts should also last 100,000 to 150,000 miles. Replacement parts before this time frame can also signal problems with the electrical system someone tried to diagnose. The only thing you should see brand new, or aftermarket under the hood is the battery. These seldom last more than three or four years. Look for leaks on the engine, transmission, differential and steering. These are time consuming and expensive to fix. Also look for burned and corroded wires and harnesses, and especially for anything not in an original harness. Wiring repairs are fine, but improper repairs are not. If the car has or had an aftermarket stereo installed, think long and hard before buying this heap. Amps, subwoofers, capacitors and the like put a huge strain on the alternator and electrical system. All that thumping is also hell on the bodywork.
Speaking of bodywork, look for excessive rust and body filler. Take the car out and wash it, checking for water leaks in the cab and cargo area. There should be no rust holes or missing body sealer and certainly no water lines in the floor, carpet or anywhere else. If there are any water leaks or damage, reject the car. Body repairs are more expensive than you might think, and can cause expensive electrical issues. Make sure all the electrical accessories work. Drive to a dark area and check the dash lights to make sure they work (An automatic car wash is great for this). These are expensive to fix on a newer car. Run the heater and air conditioner, making sure there are no strange sounds or smells. The steering, brakes and transmission should also have no surprises and operate smoothly with no noises. The engine should accelerate smoothly without missing, knocking or pinking. Check the gauges and make sure all the warning lights come on. Pay attention to the airbag, antilock brakes and brake warning light. If none of these light, or stay lit, reject the car. The airbags should be intact and the covers firmly attached. Some will sell a vehicle with blown airbags, packing the cavities with rags or paper towels. This means they'll not work when you need them most. Don't buy the car. Another one of my pet peeves is auto glass, especially the windshield. the windshield should be original to the car or at least installed correctly. Rust around the glass means the windshield will leak or pop out in a crash. They also need to be installed with a urethane caulk and bonded on a molecular level. Feel around the inside edge of the windshield and if there's anything sticky, this means someone could have used butyl to secure it. Butyl will not hold up in a crash and neither will silicone. Move along.
Now raise the hood and check the engine compartment. Look for leaks, junkyard tattoos, shoddy work, redneck repairs and excessive rust, especially on the strut towers. This is very common on Chrysler minivans 1996 through the mid 2000's and means the vehicle has to be scrapped. Excessive rust on anything structural also means the car is nearing the end of its useful life. Check the oil, which should be a clear amber color and look under the oil cap with a flashlight. Black gooey sludge means the oil hasn't been changed in a long time. Automatic transmission fluid should be a deep red in color. If it's brown or black and smells like varnish, this means it's burned. Also look at the coolant to make sure it's clean and consistent in color. If it's muddy, the cooling system is suspect. Yes, I understand there are many colors of coolant out there, but most are either green, yellow, pink or orange in color. Cooling system repairs are also annoying to expensive to fix and are the main reason motorists get stranded. Any and all cooling fans must work as these are expensive as well. You also want to walk around the car with the engine running and the lights on. Bulbs that are out aren't a huge issue for the most part, unless they're L.E.D.s or H.I.D. headlights. Blue smoke out of the exhaust pipe means the engine is burning oil and white, sweet smelling smoke means the cylinder head is warped, cracked or head gasket is checking out. Also look for obvious body damage and new parts that might indicate a crash. If so inclined, go ahead and try Carfax, but these services are a lot more limited than most are lead to believe and easily circumvented. Better to have a mechanic inspect your prospective vehicle. This is much better than any extended warranty and will save you gobs of money and time in the long run. Maranatha!