You may decide to borrow money to finance your business, either by way of an overdraft or a 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.
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.