Tipps concerning an Apple Macbook purchase?

Hi there,

I want to give a macbook to my girlfriend. Main reason herefor is, that I want to have one Max in our house, so our kid has the chance to not only get to know Windows, but MacOS as well. Since those things are pretty expensive, I want to buy a used one which is capable of getting the latest OS for the next 4-5 years at least. My girlfriend won’t be doing anything else then surfing, taking the thing with her to the university (hence at least 4h battery life).

Any tipps for specific models/years?

Thanks!