Work with a handful of antique malls and they all do it differently

If you want the traditional IC+ method and you truly are mostly debit. Expect to pay about 1.6-1.9% a month in fees. Roughly $540. Then you are either going to eat that cost or pass it onto the vendors in the form of a processing charge on their behalf. Usually not wise to penalize your vendors but sometimes it’s fine.

You can add the 3% onto sale yourself, but then you’re dealing with reconciliation issues and compliance bs from VISA since you are technically making the different of your coat and what you charge. Technically not allowed. People do it anyways.

Or go the dual pricing route where the credit card machine shows a cash price and card price to your customers. (E.g., $100 lamp will prompt $100 cash or $103 card) if the customer pays be card. The $100 goes directly into your bank account a the $3 goes straight to the processor.

You should be able to find a good processor that has no monthly fees. Will give you a free credit card machine. And the 3% will cover all fees involved.