As well as a software person I'm an arborist as a side hustle. I love bonsai and I have started a few off myself in my garden (technically this makes them 'niwaki' - in garden, rather than 'bonsai' - in a pot. I went with scots pine (Pinus sylvestris, Wych Elm - Ulnus glabra and Quercus robur - english oak) as they're all native to where I live.

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.