[burnt-resistor]

Until you slip a disc around C6, or your back or knees give out.

While "dirty hands == clean money", the problem is that it often ends in sacrifice in health and/or body that leads to involuntary early retirement.

My dad had an A/C and electrical automotive specialty shop until 1985 when that took him out in his mid 30's. He also had Agent Orange exposure in the military and exposure to various carcinogens with a culture of PPE avoidance in the automotive industry of the 70's and 80's.

[wakawaka28]

I think your dad's experience is in the minority. You could usually do that kind of work until at least your 50s. What people in his position often do is take office jobs in adjacent fields. For example, if you were a mechanic but can't work that anymore, you could work in customer service or sales since you know something about the business. If you really stick it out till your 40s and beyond, management or entrepreneurship might be more appropriate. But that isn't for everyone.