Also SAVE EVERYTHING. you never know when you are going to need that twenty year old repair manual.
No wonder we are all pack rats...
TAKE PRIDE IN YOUR WORK. It might take a little longer to do a repair correctly, but it is far less time than having it roll back in as a come back.
I have told every newbie this same thing... don't focus on speed and hard as it is don't focus on the money you make, put all of your effort into doing the job well. When you start to see jobs repeat you will start to see the times go faster and faster...
I was nicknamed "sloth" at one point in my early career, but for what it's worth... the guy that gave me the name also gave me a shop to run and apprentices to train.
Work towards owning your own business so you benefit from your labor. You still probably won't get rich and you certainly will have more headaches but it beats punching a clock your whole life.
I like this idea, but I never did go there myself...I sure did think about it a lot though. Starting off, you should spend several years in somebody else's business learning before starting your own.
Dylan, restoration and performance can pay really well... but many more will go broke trying than will succeed. Most of us make our living putting things back to factory specs on less exciting common cars. Whatever part of this you get into, the work is physical and there are no 8 hour days. Many get college degrees before or after entering this industry, and no, they are not usually engineering degrees... but that happens too. Without fail, the most successful in this industry never stop learning and never feel like they have learned enough.
There are plenty of "doctors and lawyers and such" who have nice cars and the cash/time to play with them too. If there is one thing I truly wish I had learned more about when I started... I wish I would have learned a lot more about financial matters and how some manage to retire with enough money to live the life they want (This will really matter if you try your own business, but applies to everyone). I'm not unhappy with my life or what I have done with it... I just see where I could have done better with some things.
You're young, you have a really great education so far (thank your dad), IMO you can do anything you really want to. Talk to some of the folks you know who went and did some really cool stuff when they were young enough to do it (there are a few around here). Eventually the desire to own things and make a life of your choosing will force you to make compromises...