what checks do we need to do before buying used business laptops from fb marketplace?

I am looking for a used business laptop. I have seen some listings on Facebook Marketplace in my city.

Some people have said that the used laptops they bought from Facebook Marketplace were not MDM-unlocked. I have also seen complaints about BIOS locks. I don't know the technical side very well.

What things should we keep in mind, and what checks should be done?