PayPal will take a percentage. It really depends on your usage. Kind of like a service charge. If you don't need PayPal much, they shouldn't charge you a fee. If you need a merchant type account, they'll take a certain percentage of the funds you receive. It's not bad and very competitive with other companies.
And yep, you have to transfer the funds to your checking account. It's free when done online. PayPal isn't a mind reader, so you have to participate a bit. It's such a great payment system though and most everyone trusts it. They've really worked hard for their good reputation. I encourage you to read their policies so you know what to expect.