Hey Fernand, welcome. I too worked for the coin op - commercial company for almost 30 years and was in a similar situation. It's a little scary at first, but once you get going you will like the freedom after working for someone. I actually ran the service dept for my company, so I had parts, bookeeping and other skills already. Who bought your company, one of the big boys - Coinmach or Mac Grey? They suck up all of the smaller companies in an area, then have a monopoly. Your biggest challenge - marketing yourself. Getting customers. Keeping customers. Having customers network with their friends to get you work. How you sell yourself. etc. etc.
I actually fixed everything since the early 70's. Dishwashers, refrigerators, stoves, Washers, dryers, everything. If you don't fix everything, just coin op laundry, then think about taking some classes in your area. Even if you just want to open a parts shop, you should have knowledge of all appliances. Good luck, plus you have us here to help you where we can.