FWIW, I too worked on cars all my life, as soon as people know I worked as a mechanic they always want to know if I still do side work, answer 99.9% of the time is NO. I don't need the money, and I sure don't need the headaches, or liability. I've had my own garage 2 times, and worked at dealerships as well as independent garages. My body has taken the toll, and I want to reserve what I still have left for my own purposes.....
You do what you want, but that's my answer to prospective customers.
I buy and fix trailers, and tow dollys, and sell them if I need to feel busy. Doing that I have no one that wants it yesterday, I can work on them as I see fit to.
I just ordered a 2 post 12,000 lb lift, and am going to pick it up tomorrow. I'll install it over the summer, but it's going to be for my own purposes, not for working on other peoples cars, and trucks.
BTW, I've been retired for11 years, it's working fine for me.