Getting paid
When someone opens your link they see what you are charging and pay it in SOL or USDC. Behind the scenes, that payment is sent to an address that was made for that one payment and will never be used again.
Your inbox
Your side of it is the inbox. It reads the chain, finds anything addressed to you, and shows you what is waiting. Claiming moves the money into the wallet you connected. There is no deadline, and nothing expires if you leave it sitting there for a week.
The fee
Payments carry a 1% fee, taken in whichever currency you were paid in. So a 100 USDC payment arrives as 99 USDC. There is nothing else to pay to receive money, and no monthly fee.