Hi mummies
Let's see, where do I begin...Well, to put it in short, the few most important thing to bear in mind are the STRINGS, HAMMERS, SOUNDBOARD. Strings and hammers (and felt) must be in good condition, so any damages ought to have been repaired. Soundboard must be in good condition and preferably original, as this would have meant it has stood the test of time (if talking about 2ndhand). Chips on the exterior of the wood doesn't affect the sound so that's a personal thing. Do bear in mind that if the piano is of smooth surface ie lacquered, then chips and dents can't be repaired.
If you're talking about exam model, then the height of the piano should be at least 121cm.
A piano that's <10 years...would cost at least around 4-5k (if not more) for a good Jap brand (Yamaha, Kawai). It will depend on the model (so mainly the height and how well made the mechanisms) and the condition of the piano.
Pianos generally don't depreciate steeply in price esp if it's of a good make.
As for materials, it's basically the wood that will largely affect the sound. So generally better wood is selected for the more expensive models.
Not all Kawai or Yamaha pianos are made in Japan. Some are fully made there (which means assembled there as well), some are made there but assembled in Indonesia etc, some are made purely in Indo etc. The ones fully made in Jap will command a higher price and it is normally the higher models that are fully made there.
As for a good brand that's reasonably priced...Jap has Kawai and Yamaha which are both very popular. There are Korean brands Samick and Young Chang. China brand there's Pearl River. This is probably the one and only China brand that has stood the test of time as I remember it as my very first piano (that's back in the early 80s). I wouldn't suggest buying the Korean or China brands 1sthand cos the standard is not consistent (or at least that's my experience with them). With 2ndhand that's about 4-5 years, the tone/sound is set so that's what you'll hear for the next 10 years or so.
OK, I think generally that's about it. As I mentioned before just feel free to contact me or leave your messages here. I'll try my very best to answer them. By the way, I'm based in TPY so if anyone here wants to send their children here, by all means, do contact me. Or can try out group classes for young beginners as young kids enjoy one another's company. Many music schools conduct these classes but each have their own teaching method... That's another story...
Trust your ears. Even when one's not musically trained, you'd still know what's a pleasing sound and what's not.