It's a life time of tools, a little at time. Reality is when I needed an AC compressor replaced the local shop was wanted $800-1200 for a 15 year old truck. I bought gauges, a vacuum pump, a used compressor, some AC Oil and some 134a under $400 all shipped to door. Crash course on line, never trust on source for anything in life. Swapped the compressor, pulled vacuum made sure there were no leaks. Added some oil and charged the system to factory spec per the official oem service manual. Been working for 5 years no recharge needed. My son't truck went out the next summer same deal, same type of truck. Only had to buy parts less than 100 and spend a couple of hours. Had to repair a few front end collisions from my wife and daughter, bought the wrecks and rebuilt.
I had multiple vehicles the pros had for months with out fixing, had them towed to my house and fixed them using the same manual they have.
Now I have been a techie on the clock working all over the county for most of my life. I walked away from a high end gig ( 1 of 5 in the USA) because I had enough. I've taken more training courses for different things than I care to remember. A lot of them in my "spare" time because I want to know. I stayed in "school" while working 60-80 weeks for 20+ years because tech moves fast and you have to keep up or become outdated. I started as Motorcycle mechanic, enlisted and became Aircraft electrician and the moved into the industrial world. Along the way I picked up a working knowledge of all kind stuff. I can write code, debug code (much harder) and fix most anything worth repairing. These days my time is mine and free for me to use but not collecting $300+ per hour from some big corp.
I'm not your average tractor jockey but way more redneck than most farmers and not afraid to work hard and get dirty. I've get a lot more done now that don't work on other peoples stuff, and learn new skills like welding, butchering , hunting and raising livestock.
I still have my Fluke multimeter from 30+ years ago and it works just fine, pretty sure it was well over $200 in today's dollars back in the 80's
Now to AC here not much you can do with out a set of AC gauge.