you are right that Mercedes and porche used cars are high HIGH maintenance cars; that’s why they’re dirt cheap to get them used;
just stay away from Volvos;
if you are not a DIY person stay away from all used luxury European vehicles;
they’re constantly having repair issues;
used engines are okay to put in a car as long as you have a mechanic check it out before you buy it;
THE MECHANIC MUST HAVE A FIRST RATE BIDIRECTIONAL SCANNER TO CHECK OUT ALL CYLINDERS, FUEL RAIL; INJECTORS; ECM; TCM; ETC. ETC.
IF HE DOESN’T, get another mechanic to inspect the used vehicle;
NEVER, NEVER BUY a used vehicle without a full auto technician inspection;
they will look for consistent compression in all cylinders; sludge in the oil;
making sure the trans fluid is good; etc etc;
I would never buy a brand new manufacturer engine bec you can get an entire (well maintained used) vehicle for half the price of the new engine;
Carfax is a good way to insure your used vehicle has been properly cared for;
also: if the exterior of the vehicle is 100% mint; the owner probably had enough cash to have the maintenance done properly; “probably” of course, does not mean “definitely” caveat emptor