That's what I do as well, but in my experience you need to do some serious reading before buying one. Some people claim you can buy the Txxx models pretty much blindly, but then you might be in for a surprise. The worst offender are the displays. I know these machines are office machines, but that's no excuse to use panels with deplorable contrast and brightness (look up the T410 and T420 on notebookcheck). Even current models like the T450 can come with displays with a contrast of 234:1 and brightness of 163 cd/m². Working with 'solarized' or 'zenburn' on such a panel is not fun at all, especially outdoors... Then there's the trackpad of the x40 series (T440, T540), which many people find unusable (you can change it against the one from the T450, though). Also, not all Txxx are equally serviceable. The 'p' series is much better in this regard than the 's' series, for instance. But yes, I agree that used Thinkpads are often a good choice - mostly good Linux support, very serviceable, and it is very easy to get replacement parts like keyboards, trackpads and panels for many years.