Questions about GS1 GTIN/UPC’s

Hello Amazon Sellers!!!! (Especially those sourcing from China)

I am totally brand new at this but have:

Found a product I want to sell (generic product, no brand)

Agreed on pricing with manufacturer

Started creating my listing……. (by the way, it’s been confusing that it seems I have to create the listing before I have even purchased the product)

I have all the information I need to create this listing, except I bought these UPC barcodes from barcode mania and I have come to find out that none of them work. I understand that it seems GS1 is the only legitimate way to get a UPC when selling on Amazon…BUT

I’m wondering if there is ANY way around this, like potentially buying a GTIN from another reputable place or is it true that any UPC/GTIN must be from GS1? I am working on applying for GTIN exemption but it seems like I have to already have a completed product listing to do that? (Please tell me I’m wrong) Any advice on applying for exemption is appreciated or if it’s even worth it in the long run.

Ugh, this is frustrating! I definitely can buy them from GS1 but they’re just so expensive and totally going to eat into my profit margins. Seriously, any advice!!

** Also, out of curiosity, I’m wondering if my product totally does not sell, could I delete the listing and use the same UPC afterwards? Thank you guys in advance.