One summer (like 1980) I was able to earn some money on a 4-5 week tour in the upper Midwest and Western US. I started the trip with maybe $12. Here's how I did it... bought stencils and two cans of paint (black/white) and cut a rectangular shape out of a piece of plastic. The way I earned money was by canvassing select neighborhoods and getting the housewives (usually) to let me paint their address on the curb in front of their house. I developed a rap on how it was helpful for emergency vehicles (and the pizza guy) to find your house. But mostly, I think they did cause I was a nice young man and they were intrigued by the fact that I was riding my bike with all this stuff strapped to it. The residual benefits were many… free food and places to crash, etc. I think I only charged $2 per address, but a lot of people gave me $5 or more. It is a hassle and takes time away from riding, but I did earn plenty of money and ended my trip with more than I started (which isn't saying much!) and you meet people that give you info on local environment and offer up other amenities.