Say you’re willing to work 4 hours per night (that’s a lot), 5 nights per week (that’s a lot), 50 weeks per year (also a lot). That’s a 1,000 hour work year. How much money do you want to bring in per year? The 1,000-hr year makes it easy to think about this, and to calculate. Just going at it from the other end, if you can generate $75 an hour, you can conceivably product $75,000 in a working year, just working evenings. If you’ve ever spent time as a volunteer or at a second or seasonal job to pick up some extra cash, then you know how draining that can be. If you have the stamina, then it’s a productive way to go, but if not, it’s better to monetize the things you already do or want to do so you don’t wear yourself out.