Any 16 GBs iOS device in the present day is, quite frankly, a joke!
The usable, practical data storage space of a 16 GBs iPad after formatting, installation of iOS/iPadOS and having to leave/maintain an iOS operational reserve of 2-3 GB, is between 8-9 GBs and that is it!
Your end up with an iPad with 8-9 GBs of internal data storage tops!
Really?...
What if you decide later you want to do more later with that iPad?
You basically and knowingly short changed your iPad using and storage options!
If you are looking at 16 GBs iPads, obviously you are looking at older, used devices, as Apple quietly did away with all 16 GBs iOS devices back in 2015/2016.
If you are looking at older iPad models, do yourself a kindness and, at least, look at 32 GBs iPad models.
A 32 GBs iPad after formatting and installation of iOS/iPadOS, gives a usable, practical internal data storage space of 21-22 GBs.
Which is, at least, 2-1/2 times that of a 16 GBs storage model iPad.
This gives you, at least some leeway to do other things with an iPad than just watching TikTok and Netflix.
Also, If you must purchased used devices from unknown sources, you must ask more questions of the iOS device seller, ask for more photo/images, ask if the iPad has user/iCloud activation lock and ask for photos/images/short video proof that such an iPad has been reset factory settings and shown proof of the iOS device's start up screen showing the animated, moving, multi-language “Hello” Welcome to iPad screen.
If the iOS device seller is unwilling to do all of this, pass on the iOS device and look at other iOS device sellers.
You do not want to end up with a device with Activation Lock as user Activation Lock maybe permanent and no one here in these Apple support communities NOR Apple will be able to help you or get involved with an iOS device that has user Activation Lock!
Good Luck to You!