Thanks for your suggestion. Yes, I have learned from internet that pianos have 7000~10000 parts and need professional tuning twice a year. They also need to be moved professionally.
I know a layman would often seems stupid in professional eyes. A pianist probably would not compromise the finest quality to save a few bucks.
Renting is a good option. I have contacted some rental company. Renting a Yamaha U1 is $89 per month. Shipping and delivery is $135 each time.
If my son can learn and make good progress on playing piano, I will pay happily.
