Jerry,
In my experience at i3 Detroit, knowing the material is never the biggest hurdle. If a "student" shows up with lots of knowledge, it's no trouble to swing them into a co-instructor role in the course of the class. The main thing holding people back from teaching more classes is all the overhead.
Specifically: Writing a blurb to describe the class, and creating the event on the calendar, with that blurb. Announcing it to the members, and dealing with the inevitable quibbling over date/time. If space is limited, we use Eventbrite to handle registrations, and so the event has to be created over there, too, and ticket types created and so on. On the day of the event, there are guests to welcome, waivers to sign, folks who need to know where the bathroom is, tables to rearrange, projectors to set up, et cetera, ad nauseam.
Share the work. Having a "wrangler" to help the "teacher" makes everything easier. Decouple the requirement for subject knowledge from the requirement for hackerspace knowledge.
As for money, this just came up in conversation last night. We did a survey of our members and I was astonished at the overwhelming response that we *should* charge (more) for classes, which in the past have been free or as close as reasonably achievable. And furthermore, the view that instructors should be compensated for their time. So the discussion is about how we set fee guidelines, take-home percentages, what implications this has for advertising the nonprofitness of the space, etc. I don't think we have a resolution on that, but I'm interested in thoughts from folks here, too!
-Nate-

Jerry Isdale  wrote:
>                 Hackerspaces quite often have classes, right?sometimes these are for members only, but many spaces teach public classes as a revenue stream (and to build community).but hackers are generally not teachers and teaching, especially teaching the public can be difficult.
> How have you prepared for teaching a class?Have you tried teaching when you were only a bit more advanced than the students? Sometimes this is necessary when starting a space - bootstrapping member knowledge!
> 
> Jerry Isdaleisdale@gmail.com
> 
> 
>                 