I would say it depends on the type of commercial job is it a shop front or a large office block: nursing home , etc shops would be put up like domestic properties : large commercial jobs I would negotiate with the manager to come to an acceptable price for you both , you don’t want to loose a Grand a day job for an extra fifty quid , also if doing a number of commercial jobs for the same company maybe you can make very good money on some and ok money on others , it’s all swings and roundabouts: it’s what you want to earn at the end of the day if you are happy with it then it’s fine