How long until an orchid is considered an adult?

[L. Vilas Boas]

This is more out of curiosity, because I have been considering getting young plants since they are a lot cheaper. How many years until an orchid can be considered an adult plant? And, does an orchid bloom before it is an adult?
Perhaps, the most important question: how much more difficult it is for a begginer such as me to care for a young plant? Do they demand more than an adult does between blooms?

Thank you!