Readers of The Travel Photographer blog know of my current long term involvement in documenting Chinese Opera of the diaspora; an involvement that will culminate into the production of a coffee-table book bearing the same title. It is for this reason that the blog has been recently populated with posts with excellent work of Chinese opera by travel and documentary photographers.
When you travel, saving money is often the exact same as earning. Quite often, exchanging a couple images with a hotel for a free room or a tour company for a free tour is totally worth it. In fact, when I was in Southern Africa, I did this a lot. Safaris are expensive, so I’d create a couple images for a company to use for their marketing purposes in exchange for a free safari. It really is win-win.
It's best to ask permission if you want to photograph someone, especially if you are working in close. Engage them before you pull out your camera. Learn at least how to say "hello" and "May I make a photograph" in the local language—just showing that you've made a little effort helps. Explain to them what you want to do and what it is about them that made you want to make a picture. If approached in an open and friendly manner, most people will be agreeable—many are flattered that someone has shown an interest in them and what they do. In places where there's a lot of tourism, you may run into people who are tired of being photographed—many tourists are not courteous enough to ask permission, and local people can come to feel abused and exploited. The only way to overcome this is to spend time with the people or to go to parts of the place less frequented by tourists.