The realities of the job are that only a very few could "make it" as a part-time guy. The costs of the tools, supplies, etc., the time keeping up with the latest tech, equipment, and issues, paperwork, and so forth takes a lot of time.
Also, consider this: in virtually every system I'm aware of, you, the tech, is responsible for any problems with any job you've been to for a period of time (90 days is typical). Let's say you work Sat & Sun. Six weeks ago, you did an install, and now it's Tuesday, the customer isn't getting signal, and wants a tech right away. A service call is set up for Wed or Thurs, but you don't work those days. What is going to happen is that another tech is going to be assigned that call, and if it was anything but an equipment failure, YOU are going to be charged back to pay for the other tech's truck roll. Chargebacks can eat through your pay quickly if you can't handle your repeat service calls yourself.
Also, expect your customers to call you at all hours of the day or night, because they changed the TV off of "HDMI-2" and now they have a blue screen, or because they've come home from their swing-shift job and American Idol didn't record for them.
IMO, if you're going to try part-time, you'd want to work for an independent shop. The only issue there is that the one's you'd want to work for want people with a lot of experience, not only with satellite, but with all aspects of home theater or commercial work too.