It seems to me like you need to learn more ASL before you decide to teach, even little kids. Taking a class, especially with a deaf teacher is very different from learning online or from books. The signs are only part of the language. ASL is an entirely visual language; mouth shape, orientation and sign direction all convey meaning. Signing something while moving your head in a "no" motion completely changes the meaning. Some signs are also very similar, with different meanings conveyed by mouth shape. Look up "mouth morphemes" to get an idea of what some of them are.
I took classes off and on for about three years, not a lot of classes, and not highly intensive. I cannot carry on a conversation with a Deaf person.
As for charging for classes. Look at what other similar language classes go for. Look at the qualifications of teachers and see how you compare. Are the Spanish classes taught by native speakers? Do they charge a group rate, or a set charge for a certain number of classes? Those are the things that will indicate how much language classes go for in your area.
