My ILs are notorious for buying the cheapest hunk of junk vehicle available and then spending a ton of money keeping it running, or ridiculous amounts of time broken down on the side of the road, being towed in to a garage, etc. Fortunately DH agrees with me that a reliable vehicle is worth paying a bit more for.
There's a situation going on now with DH's cousin. He drives one of the family piece o' crap vehicles, which was starting to fall apart. He decided to top off the antifreeze, and gave us a free lesson on the perils of mixing Dexcool with regular antifreeze (the two react with each other and form a gel, which will do amazing amounts of damage to your engine, transmission, and cooling system, depending on how far you try to drive. I did not know this either). So his $500 vehicle needs 800$ worth of repairs. We have FIL's hunting truck parked at our place (another piece of junk, which he "loaned" is with an air of great generosity because it's a 4x4), so Cousin is now driving that on a daily basis. All bets are off as to how long it will keep functioning before he has two vehicles rotting at his place.