DY,
1. I was referring to Rambam’s statements regarding a milchemet mitzva.
2. The Kesef Mishna only says that a rav who teaches others may receive payment. In any case, today he can publish books and receive royalties, receive a salary from the yeshiva, etc. Of course, if someone is receiving aid anyway because he cannot find a job, has a disability, etc. should go and learn to his ability.