Setup fees are FREE and there is no monthly cost.
PayPal offer a payment solution for websites looking to take payment online. They have many options available and low rates of commission on sales.
PayPal provide an all in one solution and there is no need for a separate merchant account from your bank. Payments are transferred into your PayPal account and can then be moved to your bank account.
Customers do not need a PayPal account in order to pay.
More information about PayPal can be found here.
More about their fees can be found here.