I'll just go out on a limb here and say that for Mac, his 3 things to make a little extra money (all level 4 tasks) are Warfare Lore/training with Esi and the other Tempest Sun Mages because, well, he is an expert in weapons... a true natural! Also helping out healing people with Medicine and and some helping out in the Leshy Gardens growing stuff with Nature maybe?
Just gonna make 3 DC 19 skill checks then... fail, trained success, fail. That will be 9 sp then.
Edit: Wait, that is per day. So, x7 makes that 63 silver instead. Or 6 gold, 3 silver then. Nice.