Searching for an old laptop to learn linux

I have years of experience in programming algorithms and compiling statistics. Now I would like to develop my skills and immerse myself in the world of Linux in order to get more involved with the computer itself. That's why I wanted to get an old laptop at a reasonable price to learn Linux. A friend of mine made the following suggestions: - Lenovo Thinkpad X220 - Macbook Pro 13 mid 2014 Retina What would you suggest? Preferably cheap laptops that I can work on myself in case of problems so that I can also learn from them and that I can also work with them. It should also be possible to program.