You can donate plasma for money, yes. It's not just homeless people, rarely it is. College students trying to make drinking money and such are very common. It's

You can donate plasma for money, yes. It's not just homeless people, rarely it is. College students trying to make drinking money and such are very common. It's considered less exploitative because the cells are pumped back in, with just the plasma being kept for later use. You cannot sell whole blood donations though by law, that's all volunteer.