Do you know what happens to someone who gives lots of blood as a donation?

My ex says he's going to start giving his blood for money and I'm worried about him doing this. What are the risks of him doing this often?

He says he's going to do this twice a week to make money because his friend who he lives with lost his job and so their kind of in a rut.
Do you know what happens to someone who gives lots of blood as a donation?
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