What Thinkpad Should I buy for school?

I heard the new Thinkpads are pretty reliable but they’re not upgradable and they’re expensive. I’m not sure if I should get a used one or buy a specific model that’s new. I want one that’s runs fast because I have a Acer and it takes like 10 minutes to start…can you guys help me find a laptop that will last me a long time. I want to have a health profession. Thanks!