One of my old bosses here used to do this when he lived in Vancouver. You can make a lot of money off the Chinese/Taiwanese students if you speak mandarin. They are often not confident in their english and are looking for that. As someone said before, you can also charge a premium for only girls. Often the families back in their home country are worried that they will become wild and crazy american students, speaking their language and having a girls only requirement helps a lot. I think you will not get much by getting paid through a study abroad group. He always put ads on the web where students looked in their home country before coming to study. As someone else mentioned, an ad in a local chinese newspaper should work very well, too.