You may decide to borrow money to finance your business, either by way of overdraft or loan.
You will have to pay interest on any money borrowed and there will also be bank charges due on the operation of your business bank account. Interest and charges are normally debited from your bank account every quarter - your bank will be able to help you estimate the amounts that will be due.
Card charges and PayPal
If you decide to accept payment by credit or debit card you'll need to open a 'merchant account'. You'll have to pay monthly card charges to your merchant account provider. You'll need a special internet merchant account to accept card payments yourself online. If you open a PayPal business account, or a similar account with another provider like Nochex, you will have to pay their fees too. PayPal charges seller's fees on a per transaction basis, with an additional fee due for cross-border transactions.
PayPal deducts its fees from your PayPal account. Full details of PayPal's charging structure are available on their website.