One of my old friends used to do this, not sure if he still does account selling though.
Anyway, VPNs and proxies are your friend. Amazon tends to block most of the free VPNs, but it's worth a try. Just ensure you don't swap accounts too many times using the same IP, else Amazon takes down the IP and accounts.
It can be better to use free\prepay sims instead to make the accounts. A bit of a pain in the ass switching sims, you can get a Tri sim phone, else get a Mifi router and swap the sims with the accounts esier. Plus turn on and use two factor. Less checking on the app than on the site, in most cases. Best to also get a GPS spoofing app as some apps do send telemetry.
As for fraud/scams. I tend to find, those who play the game, tend to get taken down by it. Hopefully you're just account selling and nothing more nefarious. The big boys tend to have no mercy when they catch fraudsters, and go all out to make an example of misusing their platforms.