You can find all of the information that you need regarding this at https://www.paypal.com/cgi-bin/webscr?cmd=_display-receiving-fees-outside
If you get paid for 30$ then surely their is some payment fees for that I guess around 1.75$ not really sure but something like that but if your client send it to you through gift and personal then their is surely no fees for that one
As long as they select any option under Online purchases in the Send Money section, you will be charged a paypal fee. You can view the paypal fee by viewing the details of the transaction.