I mean there are tons of publishers out there offering proofreading service. A friend of mine does this as a full-time occupation in Omotesandō. She proofreads all day and nothing else. An American boss, no uniforms, flexible work hours, and able to afford a one-bedroom in Tokyo... pretty decent as a fresh college graduate from the states. I'm not sure about the market in Taiwan, but I know there are always English speakers willing to help out when asked.
I personally speak 3-4 languages and write 2. I'm more than happy to help if someone asks (nicely).