Should I add a Plone site with the GetPaid profile?
When you add a new Plone site to the instance you have GetPaid installed in (either via buildout or otherwise), you will see that you have the option to choose the "GetPaid" profile when adding the site. This method, however, is not recommended due to complications beyond the scope of GetPaid.
Specifying an extension profile during creation of a Plone site is not recommended. It might work in some cases but it is not supported. Ideally that option should probably not even be there. This is not something that can be fixed in GetPaid.