Imo, your biggest enemy here is going to be battery life. I bought a sale-priced Lenovo t14s and I always keep a battery back in my bag just in case.
With a low power profile, having Eclipse open, a web browser to view slides/ documents and Logseq for notes my battery lasts most of the day but if I forget to charge it, it’s a pain to use pen and paper for notes.
An older laptop will have a degraded battery, and you really want maximum lifetime with multiple classes in a day.
I’m prepared to homestead if I could afford it, or live in town.
Nothing in between.