One thing business school did teach me was to start your side gig, hobby (but is it really a hobby) or business from day one.
- Separate your bank accounts. Even if you are dealing with a very small amount of operations. Don't spend out of your personal account.
- Keep track of expenses monthly. Don't wait until the end of the year. I would argue that one of the most dreaded things of the year is taxes. Speaking from experience, this part does not stress me out like it did when I was doing everything wrong.
When you can see a birds eye view on your business whether it's super part-time or full time, you will work smarter. Working smarter usually results in bigger profits for you.