What parts "fail" on a Mooney? Behind the firewall: Tank reseal. They will seep and depending on degree (service manual outlines based on size of fuel stain) you can live with a seep for years. I would not fuel my plane over half, as seep was higher in tank, unless I was flying cross-country and I could rapdly burn it off. Reseal is $7.5AMU's by the best. Doing stuff like installing strobes, putting on flap/aileron gap and hinge covers and wing base seal don't count on wings. Gear. Pucks are expensive in the nose and main gear, but again can be deferred/replaced a wheel a year. Nose gear truss will need bushings and dthese a re .2 AMU's max. If nose gear is NOT tight get it fixed. Cabin: seats/carpet/plastic/insulation are cosmetic and can be repaired/re-done BY THE OWNER...Same with windows. Brakes. The master cylinder kit was about /02 AMU's for several rubber gaskets. Same with the flap pump. Labor is/should NOT be excessive for brakes and if they are not good/get them fixed. Pads available from Spruce as are Battery (Recommend Concorde). Pushrods are pretty bullet proof. Wing-leveler rubber gaskets are NOT safety of flight and can be defeated until repaired. Step seal just holds step up. STILL way faster than a 172 with step down. Light bulbs minimal. Zeftronics voltage regulator is a MUST. .2 AMU's. The Generator is refurbishable, but we are now getting into firewall forward stuff. Oil cooler, hoses, fuel injection or carb....Ram Air seal, tires....If this stuff is 50 years old would you want to fly your family in it, or get it repaired/updated? Most of my costly stuff was self-inflicted. HID landing light, 8-pack panel,
Updating all instruments, updating radios, Engine Monitor, PC system, installing PC auto-pilot, re-doing interior (seats/plastics/carpet) installing panel GPS were ALL labors of love that made the plane a pleasure to fly safely NOT a bare minimum/legal bird. Most Mooney's are expensive because they are old and didn't have an owner that loved to upgrade/make them theirs. Avoid these planes. A Mooney is a great economical cross-county machine, but I wouldn't want to own a $30k Mooney...