Only from consenting targets (in exchange for something, or if they are not expecting to die of old age, or something). That might add up to 'nobody'; I don't have a lot of money or special access to sick/suicidal people.

I would find it tempting. I don't know how well my ethics would hold up against that kind of temptation, but the above is what I consider necessary for ethics. Given enough temptation I might go for nonconsensual acquisition from targets *I* expect to die of something other than old age, but again I have no special access to such people and don't trust I can engineer it.