Buying a piano, or, as it is referred to, a traditional or acoustic piano, is not something that is purchased without a specific need or use. Depending on the need, the purchase can be minimal, or expensive. Many people feel that starting a child on piano lessons would require a less expensive 'upright' until they show a talent and desire to continue learning. A good teacher would tell you that a better piano is more likely to be exciting for your child to play. (It is also very important that the piano is in good repair and in tune to encourage playing). You should always buy the best piano you can afford. Pianos can be traded 'up' as a need arises. The only time that there is a financial loss is when no one wants to continue playing.
A. Maybe. Some ivory is still imported (taken from elephants that have died a natural death, presumably) but it is very hard to find. Old ivory key heads and tails are frequently salvaged by piano rebuilders, however. Ask your piano tuner, or call a piano rebuilder. Perhaps they will have old pieces to sell you. (When regluing real ivory back onto a key, don't use a wet, slow setting glue like Elmer's; the ivory may warp. Use a quick drying glue like "contact cement" or the "super glues"). Yellowed ivory can be whitened by carefully scraping it with a sharp, flat chisel blade (Ivory yellows in darkness, incidentally. Keeping the fallboard up can help. So can installing flood lamps on the ceiling above your keyboard, if you're gonna get obsessive about a little yellowing ).