From what I can tell there is no fee to send or receive payments with a limit capped at $500/month. Once a CC and bank account is verified, the limit could be either raised or removed at Amazon's discretion. A business account carries charges. Details are here: https://payments.amazon.com/sdui/sdui/about?nodeId=6022#fees
The user agreement says that the difference between a personal account and a business account is that personal accounts may not receive credit card payments.