I don't believe you can sell blood or platelets. You can certainly donate those though. Both are often in short supply and are life saving.

Plasma I believe you can sell because it's then sold to pharmaceuticals that use it to make treatments and medications which are then sold back... they are also often extremely expensive.

Most locations will advertise $500 or $700 or more the first month, usually 6 to 8 collections or something in a five week period. After that it usually drops to about $15 to $30 a collection... sometimes like $15 and then if you complete another collection in the same week the second one is $30, etc.

You usually can't donate more than I think 8 times a month or something, so maybe $150 to $200/mo extra for 8 visits. Honestly when I dug into it... it didn't seem worth the 25 minute drive (and 25 minute back) eight times a month.

Edit: https://www.statnews.com/2016/01/22/paid-plasma-not-blood/ I'll be damned, much different than I thought. Still, you likely won't find somewhere paying for blood. I would be curious about the platelets though, you certainly don't want disease increasing, but as someone who has a mother suffering from acute myeloid leukemia and has probably had close to a hundred units of platelets over the last year and MANY times been told they are in short supply, she can't get them until tomorrow, or she can only have one unit instead of the two the doctor recommended, all because of supply... anything to increase their availability (safely) would be good! Same with the bone marrow!! She had a foreign donation because the registries are so much larger over there. The system is ironed out pretty well, but because of COVID it had to be transported frozen (one day of cancelled international flights could really screw things up) and the cryopreservitive is REALLY unpleasant, almost everyone becomes physically sick, including my mother, twice since it was split across two days. It otherwise is a fairly quick and straight forward process and would have been a lot less of a crappy day if she could have had that fresh. I'm surprised they don't pay $1000 or something in America for it and just spend time testing up front. The donor has to go through some processing for a few days before anyway, I would think most assays on blood work could be done in that time.