As someone who owns a T420, I can recommend it for that price. The CPU might be a bit slower and battery life might not be as good as a modern notebook but the

As someone who owns a T420, I can recommend it for that price. The CPU might be a bit slower and battery life might not be as good as a modern notebook but the keyboard is extremely nice and the overall performance with an SSD is good even for modern workflows. Just be sure to not use a Samsung 840 Evo SSD, I had bad experiences with stutter during heavy I/O that didn't happen with an HDD or Samsung 950 Pro. You can also upgrade the memory by yourself, if you need to. Remember to check if the T420 has an Nvidia Quadro card inside. If it does, the Display Port is wired to the Nvidia card and works badly under Linux and sucks the battery dry quite fast.