I also enjoy fishing as a way to make money in the Sims. It only takes a little bit of time for the skill to build up, and eventually you can be hauling in hundreds every day if you catch the right fish. Not a bad option as well, especially when paired with gardening, since the bait from the produce you grow aides in catching fish, early on.
MeestorMark--do you breed fish in an expansion pack, or is it possible to do in just regular old Sims? I play a console version--at least at the moment--and love the idea that you have. I find my unemployed Sims tend to be more boring, and would love to spruce up their lives.