Depends whether you want a business or not. If you want it to be viable expect to be working on it full time in addition to your part time job, at least for the first couple of years. It isn't just admin, you've got marketing, client queries, if you intend to do social media, accounting. There's so much more to running a business than being the technician (i.e. doing the job).

I ran a service business for 12 years, different from your idea, however. It did take a lot of time and effort. On paper, I was part-time (16 hrs) and my husband full time (40), in reality, I worked about 30 and my husband 60, and the wage we took did not reflect this.
It was stressful and the better service we gave, the more customers wanted for the same price. Many of our customer's views were that we were independent and needed the business and they were always right. We had to switch phones off after hours as people contacted us to book our services at all hours, some came and knocked on our doors.
I felt that my life was being sucked out of me, I am now working back in the emergency service I left 15 yrs ago and where once I was despondent with it, I now very much appreciate it, it has its downsides, yes but nowhere near as many as the business I ran, and I have a better work-life balance, less stress, and support from peers and management I can go to if I need to. I can also enjoy my days off, I never had a day where I was not doing any work when I had my own business, there was always something. My business took not being able to switch off to a whole new level!
I could go on and on about the downsides of running a business, and with the true benefit of hindsight I could go on and on about the benefits of where I am now in comparison, but I've been there.

The only way of knowing yourself is by taking the leap but be prepared for it not being what you wish for. It wasn't what I expected I lasted 12 yrs some dont end up lasting 1 yr let alone a few.