You can buy a disc drive later. It's $80 though, so $30 more than if you had just bought the drive included. But it's an option if you are not convinced that you want the drive now, but want the flexibility later.
https://www.bestbuy.com/product/sony-interactive-entertainment-disc-drive-for-ps5-digital-edition-consoles-model-group-slim-white/JXHQ3C2JR8
Also, if you really want to buy used, I'd get one from GameStop with a warranty. I say this because I bought a PS3 there years ago and the one I bought had cooling problems and sounded like a jet engine. I swapped it a few months later and it was pretty easy. I also say this as my first console was a PS1 bought from the Pennysaver (a booklet with ads of things for sale, oldschool Facebook Marketplace/Craigslist basically) and that one was defective from the start and I got no support for it.
EDIT: Woah what the heck, GameStop charges a lot for preowned consoles now, especially if you're not a Pro Member. That's surprising, it wasn't that bad before, wow