I've been a sysadmin for over 15 years. For the last five years, I've been organizing (and more often than not, delivering) trainings in public and private venues.
Example of a public venue -- I rent a hotel conference room for 3 days and people fly in to take a class. Or I teach at a conference, usually a half-day or a quarter-day course. Occasionally full-day.
Example of a private venue -- a company flies me in to teach their staff whom they also fly in so we are all in one room. :)
I've taught CFEngine, vi, and Time Management for System Administrators (based on Tom Limoncelli's book)
I'd do 2-6 trainings a year.
I was doing this on the side, while holding down a regular full-time job.
However, I managed to fall into a 1 year CFEngine consulting project which keeps me almost too busy to train (plug -- I have a public CFEngine training coming up in Prague in October -- USD 5K for 6 days of training for one student -- https://www.eventbrite.com/e/cfengine-3-course-and-policy-wr...)
I'd love to offer more training -- specifically I want to be able to take in a computer user and turn out a sysadmin ("infrastructure engineer" or whatever the modern term is) -- my first step toward this was working with LOPSA (Professional Content Committee) to create a sysadmin reading list (http://www.sabok.org/)
I really enjoy training, I find it quite gratifying when students light up with new-found understanding.
People often tell my training is the best they've ever had, e.g.:
"Thank you for such a great class. Been to lots of technical training and you are the best instructor I've had. Beyond standard lecture/lab your examples and willingness to help is unmatched." -- Thomas Nicholson
I've been a regular employee pretty much all my career so working on my own business full-time is new to me. I find it exciting, creative, exhilarating, exhausting. I asked the founder of Pythian (quite successful DBA/sysadmin consultancy) how he grew his company, and what was the key to his success, and he said, a RIDICULOUS amount of HARD WORK. I am finding this to be very true.