doing business while traveling - tips and suggestions?

Ages ago I saw a documentary about a man that traveled the world buying something in one locality and selling it somewhere else in the world. What he did required much research and understanding customs officers. Some of the time he made lots of money and the rest of the time he lost out because he couldn't sell all he had left. I think that painting pictures and selling them on the trip is an excellent idea. chatted to an artist living in Slovenia by the coast. He stayed in a tent and painted every day. He sold his painting to Italian tourists and those of a few other different nationalities. Teaching English a a foreign language at a summer school would be a great way to afford to travel. Likewise fruit picking is a job that is easily obtainable. I got a working holiday visa for Australia. I did work like children's nannying, collecting money for a charity and packing in a factory. Really you have to make sure that working is legal for a foreigner where you set up your business idea. That is why I loved it when I was allowed to work in Australia.