The easiest thing for me to fall into would be repair of old radios, computers, etc. I've been helping a friend deal with health issues, as an apprentice, for a long time now. I can fix pretty much anything, but I don't want to deal with Tube based linear amplifiers... the idea of playing with thousands of volts, just waiting to kill me, or burn off my digits while I'm forced to endure it because I can't let go... yikes!

In an ideal world, I'd love to just make small gears, and gear shaped objects, as a job shop. There'd have to be some dealing with the internet for orders, shipping, etc.

First step would be bootstrapping up a CNC tool cutter, so I could cut hobs, and gear shaping cutters. Then the building of the CNC gear shapers and hobbing machines. Then onward to the finishing grinders, with superfinishing at minimum.

Small -- anything less than softball sized. Spur gears, helical gears, herringbone, straight bevel, splines, gear shaped objects like flow meter turbine blades, cams, etc. Stuff bigger than watch parts, but smaller than transmission parts.

I want to be able to make Collins antique radio gears, mostly. Stuff like the gear train in this Collins R/390/UUR receiver:

https://www.chavfreezone.me.uk/racal/2018/R390-Vs-RA17L.html