Refurbished workstations upgrade guides
Used business and mobile workstation laptops — realistic upgrades after buying refurb.
Refurb ThinkPad P-series & T-series
Used ThinkPad workstations — SO-DIMM RAM and M.2 SSD are usually the best post-purchase upgrades.
Refurb Dell Precision mobile
Used Precision 7xxx / 5xxx mobile workstations — RAM and SSD upgrades; GPU/CPU fixed.
Refurb HP ZBook Fury / Studio
Used ZBook mobile workstations — RAM and SSD upgrades; check GPU tier before you buy.