I am thinking some rules are made to be broken. I would include in this someone earning $15 on a infrequent mystery shop and having to fill out a second state income tax form. I also learned a few years ago that if you spent more than 15 days in another state California considers you a non resident as far as your car registration goes. So do not vacation anywhere else for over 2 weeks or you have to re register your car and get new license plates for the rest of your trip. I actually called and spoke to someone at the time as it sounded too ridiculous to me but they confirmed it was true.
This thread inspired me today to think through this - I would like to improve my recordkeeping. I do a lot of gas station shops and it would be helpful if I had files informing me whether a station has 6 or 16 pumps - that affects if I accept it or not. And some notes in general on locations/idiosyncracies would make things go faster. I'm constantly reinventing the wheel and I want to stop doing that this year.