You've really gotten a good start on filling in the blanks.
As long as you use a C-45 licensed and insured installer for any installs requiring a permit, you can exist indefinitely without obtaining one. You would be putting a whole team of Clydesdales in front of the cart if you thought you couldn't establish your business without one. Our business is almost nine years old and we don't have one and for the cost, extra insurance, etc. to have one, it isn't worth it for the types of work that we mostly do.
In that vein, my advice is get to know your local sign hangers, electricians, etc. who will be an invaluable part of your being able to sell more than just banners, cut vinyl, coroplast signs, simple dibond signs, etc.
My other advice is establish some core values you want others to recognize you for. Ours are Integrity, Experience, Quality and Service. They come into play every single day and as soon as you treat them like cliches, you will begin losing the trust of your customers and they will view as just another typical business and not the unique and committed professional you hopefully are striving to become.
As the years go by in your business, those fundamental values are as important in the eyes of customers as how many rad photoshop effects you can cram into one wrap.
