Interesting that you say that. I had Imaizumi Sensei and his wife at Mayda and I's house for the weekend (a couple of weeks ago) and we were talking about how certain people able to study as they did. Imaizumi Sensei explained that the first son had the family obligation to follow in a family's tradition and that this expectation was difficult to get out of. The subsequent boys, like Imaizumi Sensei, were allowed to follow other paths. Imaizumi Sensei's family helped to support him when he quit his job and became a full-time Aikidoka at the Hombu Dojo. Your family had to have money to subsidize such ventures for sons other than the first born son.
I think it was Ellis Amdur who told me that Kuroiwa Sensei was one of the few deshi at Honbu in the post war group from a more working class background.