Got my '86 420SEL in December 2003 from the original owner's family, for $2000; 146K o n the clock, not running, no records, but I have pretty-much known it since new. Got all the M&Ms out from under the seat, kids had roughed up the interior a little as it morphed from a classic to an old car, new fuel pumps got it running though. I have probably spent $3000 plus my labor, fixing mostly little things: sunroof; brake reaction joints;steeering damper; radio; antenna; repaint alloy wheels; new tires; timing chain and upper guides, along with cam oiler tube plastics, misc. hoses, etc; fuel injectors and seals; spark plugs; ACC fan motor; ACC control box; replaced plastic front grill which was probably bird-broken; left-rear power window (needed the plastic piece in the mechanism); cleaned power seat switch; power steering pressure hose and filter/fluid; replaced three door checks; fuel pumps and filter; idle control box; antenna switch; all fuses.
So far.
Has 153K on it now. Would I do it again? Hey, it's a hobby. If it isn't fun, there's no reason to do it; drive a Taurus.