He is not going to teach in any school, just privet students mostly for speaking. The students are from different range of age and education.

Sounds like your friend shouldn't be teaching if he has no inkling on where to get the materials, books, etc.
There's lots to choose from. Since tutoring is a more personalized experience, the election of contents, books, etc. depends on the tutoree. Why are they taking ESL lessons? Survival skills? Fluency? Better understanding? For work?
One first point of reference would be the Canadian Language Benchmarks.
Check www.language.ca
If your friend were a certified instructor, he should know what books to get.