Check the buyer’s guides on r/thinkpad. Typically you’re looking at T or X series, with T giving the most flexibility. T410 to T430 can be had for less than $20

Check the buyer’s guides on r/thinkpad. Typically you’re looking at T or X series, with T giving the most flexibility. T410 to T430 can be had for less than $200 and should be fine for server use. The numbering scheme is Txy0, with x the screen size (4 for 14), b the Core i generation (0 is core 2 duo).