Bought a cheap very old piano a couple of yours ago, heavily out of tune. Since it was quite a lost case to begin with I decided to do exactly what the internet tells you not to do and tune it myself. Of course this doesn't compare to the ears, experience, and material a professional tuner would bring to the table, but if your piano has got nothing to lose (like mine), and you're willing to put in the time and effort, this is worth it. I'm still using my piano years later, obviously not a price beast, but I love the fact that I tuned it myself and still play it.