Okay stop everything... I'm about to agree with Danny.
I worked HVAC for ten years, if you are looking for hot, dirty, dangerous, nasty yucky, uncomfortable work... go for it! Oh and half the people you will be working with will be raging A-holes.
There is a reason it is so hard to find people to do the work.
When I quit twenty years ago and went back to school I did side jobs to support myself, like you said I was honest and hard working, knew what I was doing, showed up on time, cleaned up after myself... after a couple of months of that just by word of mouth people were fairly begging me to work on their houses. I could have made a comfy living working like that.
The only good way to make money in HVAC IMHO is to get your contractors license, open a shop, and hire a couple of young bucks to do the dirty work. My dad did very well at that (I was one of the young bucks)
I hear pumping out septic tans pays well too.
No, I'm not bitter!