Are you affiliated with a company, or will you be an independent, offering a wide range of insurance plans? If the former is true, certainly the company has all sorts of helps for you plus you can hobnob with other agents to find out how they got started and mistakes they made that you will avoid making.
An insurance agency is a small business. Go to your local public library to find books on starting a small business. Ask for help from a reference librarian if you can't find any. I know the books are there.
Ask the reference librarian about village, township, county, and state laws/ordinances that will affect your business and if you have to register a DBA ("doing business as") with any of them (and pay $$).
Ask the reference librarian if there is still exists a book on starting an insurance agency, There used to be one in a three-ring binder format, but it may have gone the way of the oxcart. If it still exists, you might want to get it through interlibrary loan. Or there may be a much more recent version published.
Ask for the phone number for SCORE. It's a helpful organization of retired business executives. There is an 800 number for them. They probably have a web site. Aha!! They do --
SCORE "Counselors to America's Small Business" and a handy-dandy site it is too!
Best wishes and let us know how you are doing.