>>512972920
Oil changes have pretty much always been very cheap. Filter included. Back in the day they would even change your valve cover gasket while checking the valve clearance, everything done, oil included for under 100 bucks. Nowadays of course no need for it because all valves are hydraulic. Car manufacturers started to compete with lower maintenance costs long time ago. Things don't get fucked up easily but when they do, it will be very expensive. It was a good call to become a car mechanic. Literally saves thousands a year.
My first advice to all DIY mechanics is to buy an OBD2 scanner. Sometimes it actually helps. I was tracking a supposed electric failure in the fuel pump (Audi A6 Quattro with V6 automatic, my own car) because the car wouldn't start, I went through all the wires with a multimeter for a few days until my neighbor brought his OBD2 and it immediately said my battery power was slightly less than 12 volts which had initiated the immobilizer. The car started after I charged the battery over night.