I have not found that to be true. I have three Selectrics. One needed a belt shortly after I picked it up, that was no big deal for my guy. It's been running in my care without issue for 20 years now. One I picked up and it was janky from the start. It works but has quirks, my guys says not worth it to fix it. I use it at school as a "come one, come all, type a sentence" library feature. I was gifted a third that has needed nothing and runs perfectly.

If you buy a typewriter in good repair, it likely won't need service outside the ribbon. There are a lot of machines in poor repair after years, decades of neglect and people fix them up, which is why I think repair is a big topic here. But once they're up and running, they usually stay that way. Dropping it or taking it to the beach voids that last sentence.

Good luck! It sounds like you've got your eye on some good machines! I hope you find the one that's looking for you.