“What do I need to know about 3D printing before starting or buying a 3D printer?”
You know people ask that question a lot how ever I personally find that 3d printing is a learn as you go (or rather run in to issues) type of thing. My personal answer is for a first 3d printer (buying wise) is don’t go too cheap how ever don’t go to expensive either (assuming personal printer not company). If your looking at printers for a company go with something that has a good reputation with strong company / user support. If your looking for yourself look for something with at least a strong user community behind it.
Personal (non company): I’d go with something like a Wanhao (low price), CR-10(low price), Prusa(mid range)
Professional: I’d spend out the money for something like the Ultimaker(high end)
Why I’ve chosen this is simple you don’t know how well the bug will hit you so if you don’t like it your not in too deep out of pocket with the cheaper printers (but don’t go too cheap). If you like it you can always sell your original printer and upgrade to the Ultimaker or other higher end products. Nothing in 3d printing is perfect no matter what you will have to stop scratch your head then figure it out (even with high end printers).
At work we have a $6000 3d printer that prints no better then my Wanhao that costs $300 (well ok with the mods that make it better more like $400, in my case a thicker y-carriage and z-brace mod, I have other mods but those 2 I’d say are the best 2) so time, learning, tinkering you can make a fairly cheap printer go far.
Remember we all have our opinions and thoughts this post is mine from my own limited experience of usage. Take it with a grain of salt.