Should there be a maximum age limit to change trades?

This is silly. Each individual is different. If he is moving only for hours and pay with no interest in the work he will be a burden just as so many young apprentices have been while they take a year or two to figure out they want to do something else. Is that burden-less? If he truly has an interest and he may have some transferable experience he may quickly become your best tech.

Equal opportunity to all, notwithstanding age or other personal attributes / persuasions. Often Today professionals are working 'productively' through their Seventies, many into their Eighties. I could cite several professional Colleagues as examples of the previous statement, but I don't want to prejudice their co-workers against them! I started doing Half-Marathons at 65YOA (and have completed 7 of them, all in the 3:20 to 3:08 range-with improvement every year!). I qualified as an SCCA (Sports Car Club of America) Driving Instructor at 70YOA with a highly-modified 2002 Subaru Wagon which has been officially clocked at 166MPH! Paul Newman raced at a World-Class Level with competitive performance times into his eightieth year. Many of us actually "enjoy" what we have done for our entire careers-48YRS and counting in my case! Clients can vote with their funds and many will still cast their vote for DEMONSTRATED EXPERIENTIAL $UCCE$$! Robert E. Sherman ISA Life Fellow (2002) Editor: "Analytical Instrumentation: a practical Guide" (1996)-Second Edition will be published 2018. Author: "Process Analyzer Sample-Conditioning System Technology" (2002)-prompted Swagelok to commission a follow-up volume in 2013.