About being multi-skilled re various jobs. When I taught high school I noticed that the future tradesmen came from the classes which were average. If these people could weld, fabricate, etc., it couldn't be that difficult. Owning a gym often requires various tasks and it wasn't long before I learned how to weld and use simple machine tools to make gym equipment. I graduated to having an engineering factory complete with big lathes, milling machines, auto bandsaw, 3 Morse Taper Radial Drills and everything else needed to fabricate gym equipment. I got manuals and learned that way. Nowadays it is easier and better to watch and learn from YouTube videos.
Over the years we have moved gyms. So I had to draft plans for council approval. Then there was some building to do such as partitions. Some simple plumbing, tiling, electrical work, and installing and shifting things like mirrors and equipment. You soon become a jack of all trades if you own a gym for decades.
Computers were easy to use and I even built my own super computer a few years ago. Well, super for me. 48 Gb of Ram for example.