It can be as low as 3% charge for accepting paypal payments. There is a flat fee for each transaction + 2.9% of the total amount, so if you accept one big payment, say £300 they only charge you 3.1%, but if the £300 is made up of 30 payments of £10 then the overall charge is more.
The security setup is more for buying stuff using paypal, I don't think you have to do anything to accept a payment, but yes as Revhead says there is another charge for withdrawing small amounts, which is fair. Far better to let the payments ride and they'll get used up next time you buy something using paypal.
Bear in mind all credit card companies charge up to 3% for accepting credit card payments so PayPal is no different. It's an excellent service which takes the hassle out of selling stuff on ebay. I only accept bids from people who have a PayPal account - you can select this in the options when you create your ad on ebay. Cheques are just a pain, which the banking world are doing their best to irradicate completely.
