I rented a unit and the guy next door (his unit was much bigger) came over to suss me out, see who I was etc, we got talking.
He fixed gearboxes (that's all he did); all the local garages, large and small, would send him the car, he would take out the gearbox, strip it, fix it and put it back in. He said he charges around £2k per gearbox.
He told me that he retired early, a while back, sold his business, and moved to Spain, he bought a large plot of land as his wife kept horses. One day he was mowing his huge lawn on his ride-on mower and 'had a moment' where he wondered what the hell he was doing with his life! A guy in the local village had a problem with his gearbox so the guy fixed it.
He has now moved back to the UK, started up a new business and fixes gearboxes again, his daughter works with him too.
I guess retirement is different things to different people!