It's possible to find a typewriter that was properly prepped for the decades-long hibernation it was likely rousted from, just before you found it at a garage sale or online. It's much more likely, however, that the machine you got or will get, last watched television in black and white before being unceremoniously shelved in a damp and dirty garage.
Those that lived luxuriously may just need a new ribbon and a puff of air to clear a few cobwebs. For the rest of them, it's a thing, coming back from the dead. Though they were built to last, they were not built to automatically fend off water and rats, airborne bacon grease and the dust that sticks to it. They definitely weren't built to fend off children hammering on their keys with Tonka trucks and raging little fists.
As hard as typewriters can work, don't forget that there are tiny little mechanisms inside of them that perform complex functions and are connected through a networks of pulleys, springs and levers to other elements doing the same thing. And sometimes a function is only as good as the weakest link in the chain.
Sometimes it matters to identify something that was wrong with a machine before it was shelved, compared to something that was caused by neglect and age. Sometimes one can tell exactly what caused someone to give up on a machine years ago, and sometimes one can even see the damage someone did trying to fix a problem using kitchen utensils, and maybe even that Tonka.
But in the end, it doesn't matter. Things need fixed. And things that need fixed need more people who can fix them. With a shortage of experienced people to solve complicated issues, collectors are taking it upon themselves to dig in and figure things out. Thankfully there is information out there, as well as people who are willing to help with good advice when the going gets tough.
Even for typewriters that avoided any physical damage and are just dirty, the deep cleaning process is still a complicated experience. There is no uncertain amount of dismantling that needs to be done in order to access dirty elements that were seemingly engineered for the exact purpose of not being accessible. In fact, there are even user and service manuals that proudly state in plain language that certain design aspects were introduced to keep non-professionals out of the machines. They did not see the day when few people could actually fix anything, and professionals would be scarce. They also likely didn't see the day we'd be communication in grunts and clicks with LOLs and emojis.
But, here we are.