We tried to bank cord blood for my first child with a public cord blood bank, but we got a letter from them a few months after the birth that the volume wasn’t sufficient - so yes, there is a minimum amount, for the public banks at least.
I’m pretty sure if you want to collect the cord blood properly the birth needs to be done in a hospital. The OP has stated previously that he and his wife intend to deliver at home with a midwife. Not sure if that’s even workable, but IANAD.
Actually, I don’t think that’s true. I’ll bet there’s a pretty high overlap on people who want home births and also to bank their cord blood. Or at least eat it.
I don’t doubt that. I’ll pass.