You can find some online HVAC courses and get a certificate in six weeks. But, of course, it would be better if your son attended the HVAC school. But, because of the pandemic, a lot of schools are closed. Anyway, I think there must be a way. I can recommend you this site hvacschools411.com, you can find there some useful information about HVAC training and HVAC schools from all states. I got my license three years ago but before I got the license I worked sometimes as an HVAC technician with my dad who was licensed already. My dad taught me everything I should know about this job and I'm really grateful for that.