I see a lot of discussion that includes used ThinkPads, there's one caution I'll give if you go that route: avoid the __40 models (T440, T540, etc). I've not used an X240 but the TouchPad on the larger models is unusably bad.
That's actually where it is worst. That generation of Thinkpads omits the physical buttons you normally use with the trackpoint, instead using soft buttons on the "click" style trackpad. It makes both functions much less usable.
