But I am somewhat conflicted because as awesome as they look, all that aesthetic comes from doing the exact opposite of what a tree needs. Deliberate wounding at non-meristematic sites to create deadwood, binding roots into and using wires to manipulate the structure and keeping the tree at a juvenile isolated state. Basically it would make Alex Shigo shudder in his grave.
That being said, if anyone is in their twenties and looking for a nice future hustle pension, then start off some bonsais today. In forty years, if you can keep them going, with a hundred or so you could be sitting on 300K plus of stock. The trees will teach you a lot (notwithstanding the above sentiment on treating them brutally) in terms of patience, planning and delight in aesthetic.